Fence Calculator

Purpose and model boundary

This calculator counts the materials for a fence round a yard that you draw. You draw the yard's outline, a closed shape, and on it you mark each opening, a part of a side where no fence stands (a house wall, a driveway, a road or a neighbour's fence), and each gate. You choose the fence style, the fence height, the post spacing, size and depth, how the posts are set, the rails in each section and the length the rail boards are bought in, the widest gate hung as one leaf, whether to add post caps and a kickboard and, for a privacy or picket fence, the picket width, the gap between pickets and the waste. The spreadsheet returns the posts, counted once each by where they stand (corner posts, end posts, gate posts and the line posts between them), the sections, the rails, the pickets or the panels, the gate hinges, latches and drop rods, the posts set in concrete and the bags of concrete to set them, the length of each post and of each picket, a buying list in stock lengths (the posts and the rail boards), the picket fasteners, the rail brackets and, when chosen, the post caps and the kickboard, the lengths of the fence and of its outline, and the area the outline encloses. It is not a fence design, a survey, a code or permit check or a cost estimate. Slopes, curves, frost depth, soil, wind load, pool-barrier, boundary and height rules, hardware sizes and prices are not modelled.

Inputs and units

The drawing is the first input. Its outline is sent as an ordered list of 3 to 100 points, round the yard in either direction; side k goes from point k to point k + 1, and the last side back to point 1. The outline is closed: every side is fence unless an opening removes it. With Fence ▾ on the drawing you open a whole side or part of one, and add gates. The drawing writes up to 20 openings and up to 20 gates, each on one row with its ID (O001, O002, and so on for openings; G001, G002, and so on for gates), its side, its start measured along the side from the side's first point towards its next, and its length (an opening) or its width (a gate). An opening lies on one side, and openings may touch but not overlap; a gate goes on fence: it never overlaps an opening or another gate, and its width is taken out of the fence. A corner that an opening turns is opened on both of its sides, one row each. The US/Metric switch on the drawing chooses the unit the points and rows are written in, feet for US and metres for Metric, and the unit of every length and of the area.

The inputs beside the drawing are:

• Fence style: Privacy and Picket fences are counted in pickets, Panel fences in panels, one per section, and Rail fences in rails only, such as split rail or post and rail. Every style is counted in posts, sections and rails.
• Fence height, in feet (US) or metres (Metric): the top of the pickets, boards, panels or top rail, and of the posts. Each picket is this long, and each post is this plus its depth in the ground. It sets those lengths only.
• Post spacing: the largest distance between post centres along a stretch of fence, in feet or metres.
• Post size: 4x4 or 6x6 in US, 90 mm or 140 mm in Metric. A 4x4 is 3.5 in square and a 6x6 5.5 in square; the Metric posts are 90 and 140 mm square. It sets the concrete only when a hole diameter is entered.
• Post depth in the ground, in feet or metres: each post is the fence height plus this, and the concrete follows it.
• Set posts in: concrete at every post; concrete at the gate, corner and end posts only, the line posts set in tamped soil or gravel; or no concrete. Soil and gravel are not counted. With no concrete the post size, the hole diameter and the concrete bag are hidden and not needed.
• Hole diameter, optional, in inches (US) or centimetres (Metric): leave it blank for the typical concrete a post, or enter it to count the concrete for that hole.
• Concrete bag: 40, 50, 60 or 80 lb in US; the same bags labelled 18.1, 22.7, 27.2 and 36.3 kg in Metric.
• Rails per section: the horizontal rails between two posts, counted for every style, panel fences included; 0 suits panels that come with their rails.
• Rail board length: the length the rail boards are bought in, 8, 10, 12 or 16 ft in US and 2.4, 3.0, 3.6 or 4.8 m in Metric. The kickboard is bought in the same length.
• Post caps and Kickboard (rot board): Yes or No.
• Picket width and Gap between pickets, in inches (US) or centimetres (Metric), used for Privacy and Picket fences only: each picket and its gap take up the width plus the gap along the fence. A gap of 0 is pickets that touch.
• Picket waste, for Privacy and Picket fences: extra pickets for cutting, splits and rejects.
• Widest gate hung as one leaf, in feet or metres: a gate wider than this is hung as two leaves.

Every size and length has one field for each system, each with its own default: a 6 ft fence, posts every 8 ft, 4x4 posts 2 ft deep, 60 lb bags, 8 ft rail boards, 5.5 in pickets with a 0.5 in gap and gates up to 4 ft on one leaf in US; 1.8 m, 2.4 m, 90 mm posts 0.6 m deep, 27.2 kg bags, 2.4 m boards, 14 cm, 1 cm and 1.2 m in Metric. The Metric defaults are round figures, not conversions: 6 ft is 1.8288 m, 8 ft is 2.4384 m, 2 ft is 0.6096 m, 5.5 in is 13.97 cm and 4 ft is 1.2192 m. The style, the post setting (concrete at every post), the rails per section (3), the waste (5%) and the post caps and kickboard (No) are the same in both systems, and the hole diameter is blank. Switching between US and Metric shows the other system's fields with their own values and never converts a number you typed; the value you typed for the system you left is kept for when you switch back, and it is not sent while it is hidden. The drawing converts its own points and rows when you switch.

The page opens on a 60 by 40 ft yard fenced all round, with no opening and no gate: 26 posts, 78 rails, 420 pickets and 52 bags of concrete. Open the house side and add gates with Fence ▾. The defaults, and the spreadsheet's own figures below (the typical concrete a post, 2 hinges for each leaf, 1 latch for each gate, 1 drop rod for each two-leaf gate, 2 fasteners for each picket on each rail and 2 brackets for each rail), are typical figures for review before use, not values from a code or a standard.

Governing relationships

A stretch of fence is a piece of a side between two neighbouring items (openings and gates) or corners that is neither an opening nor a gate. A side with nothing on it is one stretch, the whole side. A piece of 0.00001 in or less is not fence.

Posts. Every post stands at a point of the outline or at an end of an opening or a gate, and each is counted once, by where it stands:

• At each point of the outline: no post when both sides that meet there are opened; a gate post when a gate on either side reaches it, flush with the corner; a corner post when fence continues on both sides; otherwise, fence on one side and an opening on the other, an end post. Every point the fence or a gate reaches is a post, a point on a straight side included; the spreadsheet does not merge two sides that happen to be in line.
• At each end of an opening or a gate inside its side: a gate post at either end of a gate, whatever else meets there (an opening, another gate); an end post at an end of an opening with fence beyond it; no post where two openings touch. Where two items touch, one post stands between them: two gates side by side share one gate post.
• Line posts stand between those posts at no more than the post spacing. Each stretch is divided into sections, at least one:

Sections = stretch ÷ post spacing, rounded up to a whole section, and never fewer than 1

Line posts = sections − 1 on each stretch

Posts, all = corner posts + end posts + gate posts + line posts

So a fence has as many posts as sections plus gates plus one for each run of openings (one opening, or several touching end to end, across corners too); a closed fence with no opening has as many posts as sections plus gates. Terminal (end, corner and gate) posts with line posts between them at no more than a set spacing are the common practice of the guides listed under the references. This calculator counts each post once by where it stands.

Post length = fence height + post depth, every post, gate posts included

Rails, pickets and panels, on the stretches only (a gate carries none):

Rails = sections × rails per section, every style

Pickets = stretch × 12 ÷ (picket width + gap), rounded up to a whole picket on each stretch, in US units; in Metric the stretch is multiplied by 100, the centimetres in a metre. The stretches' pickets are added, and that is the pickets before waste; then

Pickets, with waste = pickets before waste × (1 + waste), rounded up, for Privacy and Picket fences, and 0 for Panel and Rail fences

Picket length = fence height for Privacy and Picket fences, and 0 for the other styles

Panels = sections for a Panel fence, and 0 for the other styles

Gates. A gate wider than the widest gate hung as one leaf is hung as two leaves, meeting in the middle; a gate at or under it is one leaf. For each gate:

Hinges = 2 for each leaf

Latches = 1

Drop rods = 1 on a two-leaf gate, which holds one leaf fixed, and 0 on a one-leaf gate

Concrete. The posts set in concrete are every post, the gate, corner and end posts only, or none, as chosen. Each one takes the concrete for its hole:

• With the hole diameter blank, the typical concrete a post: 0.9 cu ft (25.5 L) for a hole 2 ft (0.6 m) deep, which is 2 bags of 60 lb (27.2 kg), taken in proportion to the post depth: concrete a post = 0.9 cu ft × post depth ÷ 2 ft (in Metric, 25.5 L × post depth ÷ 0.6 m).
• With a hole diameter entered, the hole's net volume, the hole less the post, over the post depth: concrete a post = (π ÷ 4 × hole diameter² − post width²) × post depth, the post at its actual size (3.5 in for a 4x4, 5.5 in for a 6x6, 9 or 14 cm in Metric). No allowance is added: add extra for spillage, an uneven or belled hole, or a frost footing.

Concrete bags = posts set in concrete × concrete a post ÷ the bag's yield, rounded up once. The yields are 0.30, 0.375, 0.45 and 0.60 cu ft for the 40, 50, 60 and 80 lb bags, the manufacturer's published figures; in Metric the same bags yield the same volumes in litres (8.5, 10.6, 12.7 and 17.0 L). With no concrete the bags are 0.

The buying list. Every post is bought at the shortest stock length at least its length, 8, 10, 12, 14 or 16 ft (2.4, 3.0, 3.6, 4.2 or 4.8 m): Posts at the stock length = posts, all. A post longer than the longest stock length leaves both at 0, with a CHECK: line, so that it is ordered to length.

Rails are bought as boards of the rail board length, counted stretch by stretch. Each board is cut into rails a section long, as many whole sections as one board covers (a 16 ft board makes two 8 ft rails); the pieces of all the rails on a stretch are pooled, so on each stretch Rail boards = rails per section × sections ÷ the sections a board covers, rounded up. A section longer than a board takes two or more boards a rail. Boards never cross a gate, an opening or a corner, and no cutting waste is added. A Panel fence takes no rail boards: its panels carry their rails. Rail boards a full section takes is the same figure for one section a post spacing long: 3 rails on 8 ft sections are 3 boards of 8 ft, or 1.5 boards of 16 ft, one board serving two sections' rails.

A kickboard, when chosen, runs along the bottom of the fence, between the posts like one more rail: Kickboard length = fence, not counting gates, and its boards are counted as the rail boards are, with one rail a section.

Fasteners and small parts.

Picket fasteners = 2 × pickets before waste × rails per section, 0 for Panel and Rail fences

Rail brackets = 2 × rails, one at each end of a rail

Post caps = posts, all when caps are chosen, and 0 otherwise

Lengths and area. Outline length is the sum of the sides; Left open the sum of the openings; Fence line, through its gates = outline length − left open; Fence, not counting gates = fence line − the gates' widths; and Area inside the outline is the area the outline encloses, by the shoelace formula, in sq ft (US) or m² (Metric).

Every count is rounded to six decimal places and then rounded up to a whole number, which keeps a count that is whole on paper whole in the spreadsheet: a 16.8 m side at 2.4 m is exactly 7 sections, but 16.8 ÷ 2.4 is 7.000000000000001 in floating point, and unguarded IEEE arithmetic gives 8; 9.3 m of 14 cm pickets with a 1 cm gap is 62 pickets before waste, where unguarded arithmetic gives 63; and 100 pickets with 10% waste is 110, where unguarded arithmetic gives 111. The waste applies once, after each stretch has been rounded up to whole pickets. Every length and the area are rounded to nine decimal places, so the order the rows are listed in never changes a figure.

Calculation sequence

1. The spreadsheet reads the unit system, the outline, the openings and gates tables and the fields of the selected system.
2. It checks the outline, every row of the two tables and every input, as described below; a blank row is not an item, wherever it sits in its table.
3. For each side it finds its stretches, from the side's first point to its first item, between neighbouring items, and from its last item to its end, or the whole side when nothing is on it.
4. For each point of the outline and each item end inside a side, the post that stands there, if any; for each stretch its sections, line posts, rail boards and, for a privacy or picket fence, its pickets.
5. The totals: the posts, sections, rails, pickets before waste and with waste, panels, the gates' leaves, hinges, latches and drop rods, the posts set in concrete and the concrete bags, the post and picket lengths, the stock length, the rail and kickboard boards, the fasteners, brackets and caps, the lengths and the area; and the gate schedule, one row for each gate in the order of its ID number.
6. The status line is chosen. When it begins NOT VALID:, every figure reads 0 and the gate schedule is blank.

A worked check. A 60 by 40 ft yard drawn clockwise from its top left corner (side 1 the top, 2 the right, 3 the bottom drawn right to left, 4 the left drawn bottom to top): the house takes the whole of side 1, opened; a 12 ft driveway is opened on side 3 from 20 ft; a 4 ft gate stands on side 4 from 10 ft. A 6 ft privacy fence with posts every 8 ft, 4x4 posts 2 ft deep in concrete at every post, 3 rails, 8 ft rail boards, 5.5 in pickets with a 0.5 in gap and 5% waste:

• The stretches are side 2 whole (40 ft), side 3 from 0 to 20 ft and from 32 to 60 ft (20 and 28 ft), and side 4 from 0 to 10 ft and from 14 to 40 ft (10 and 26 ft): 124 ft of fence, a fence line of 128 ft (200 ft of outline less 72 ft left open) and one 4 ft gate.
• The points: point 1 and point 2 each have fence on one side and the opened house side on the other, so each is an end post; points 3 and 4 have fence on both sides, so each is a corner post. Inside the sides, each end of the driveway has fence beyond it: 2 end posts; each end of the gate is a gate post: 2. So 2 corner posts, 4 end posts and 2 gate posts.
• The sections: 40 ÷ 8 = 5; 20 ÷ 8 = 2.5, so 3; 28 ÷ 8 = 3.5, so 4; 10 ÷ 8, so 2; 26 ÷ 8, so 4: 18 sections and 4 + 2 + 3 + 1 + 3 = 13 line posts. Posts, all: 2 + 4 + 2 + 13 = 21, which is also the 18 sections, the 1 gate and the 2 runs of openings (the house side, and the driveway).
• 18 × 3 = 54 rails; the pickets before waste are 80 + 40 + 56 + 20 + 52 = 248, and 248 × 1.05 = 260.4, so 261; 21 × 0.9 ÷ 0.45 = 42 bags; the 4 ft gate is one leaf, with 2 hinges and 1 latch.
• Each post is 6 + 2 = 8 ft, bought as 8 ft posts: 21. No section is longer than 8 ft, so each 8 ft board makes one rail: 54 rail boards. 2 × 248 × 3 = 1,488 picket fasteners and 2 × 54 = 108 rail brackets.
• With 16 ft boards, a board makes two rails where a section is 8 ft or less: 15 rails on side 2 take 8 boards, and the stretches take 8 + 5 + 6 + 2 + 6 = 27 boards. A kickboard along the 124 ft of fence takes 3 + 2 + 2 + 1 + 2 = 10 of those boards.
• With concrete at the gate, corner and end posts only, 8 posts take 8 × 0.9 ÷ 0.45 = 16 bags; with a 12 in hole round each of those 4x4 posts, each holds (π ÷ 4 × 144 − 12.25) × 2 ÷ 144 = 1.40 cu ft, and the 8 posts take 25 bags.

Worked example 11.5.3.4 of the requirement this calculator was built against, 400 ft of split rail along a road frontage with the field's other three sides opened, posts every 10 ft and two rails, gives the printed figures: 40 sections, 41 posts (2 end posts and 39 line posts), 80 rails and 82 bags. Four of the requirement's examples are drawn with their gates placed on the fence and differ from the printed figures, for the reasons given under Assumptions and limitations.

Outputs and interpretation

Posts, all, Gate posts, Rails, Pickets, with waste, Panels and Concrete bags are the headline figures; pickets are shown for a privacy or picket fence and panels for a panel fence, and a rail fence has neither. Corner posts, End posts, Line posts and Sections, the posts set in concrete, the post and picket lengths, the pickets before waste, the buying list (the posts at their stock length and the rail and kickboard boards), the picket fasteners, rail brackets and post caps, the gates' count, hinges, latches and drop rods, and the four lengths and the area are the details: the lengths in feet (US) or metres (Metric), the area in square feet or square metres, and the others whole numbers, except the rail boards a full section takes, which may be a fraction. The gate schedule lists each gate in the order of its ID number, with its side, its width and the leaves, hinges, latches and drop rods it is hung with; its columns add up to the gate figures.

The page shows every figure to at most two decimals, and every figure is the spreadsheet's own. The drawing shows the lengths of the sides, the openings, the stretches and the gates as you draw them, and the area the spreadsheet returned; it never shows a post, section, rail, picket or panel count.

The 3D view. After Calculate, 3D on the drawing shows the fence at its height: the posts by kind, running into the ground to their depth, the concrete round each post set in it, the rails, the pickets (pointed on a picket fence) or the panels, each gate's leaves, one or two as the gate schedule says, and the openings. It draws only what you entered, what the drawing measures and what the spreadsheet returned, and each family only when the members it lays out equal the spreadsheet's count: the posts by kind and the sections, the rails, the pickets before waste and the panels, the posts set in concrete, and the gates against the gate schedule. A family that does not match is left out with a note, and before Calculate, after a change or under NOT VALID: only the fence line, the openings and the gates are drawn. Gates are drawn closed, the ground is drawn flat and the styles are schematic, not materials or colours; the pickets drawn are the pickets before waste. The concrete is drawn as a cylinder to the post depth, as wide as the hole diameter you enter, or, with the hole left blank, as wide as a hole that holds the typical concrete a post round that post; it is a picture of where the concrete goes, not of its volume or the bags. Hinges, latches, drop rods, fasteners, rail brackets, post caps and the kickboard are not drawn.

Validation and status logic

The status line is the spreadsheet's own verdict. It is the first of these that applies (the CHECK lines read 4 in in US and 10 cm in Metric; each message that names an item names the one with the lowest ID number that qualifies, so the order of the rows never changes the message):

• NOT VALID: choose US or Metric
• NOT VALID: draw at least three outline points
• NOT VALID: every outline point needs both coordinates
• NOT VALID: outline points must fill consecutive rows, with no blank row between them
• NOT VALID: outline point k is more than 83,333.33 ft (1,000,000 in) from the origin along an axis (in Metric, 10,000 m (1,000,000 cm))
• NOT VALID: outline points k and k + 1 are the same point; delete one
• NOT VALID: sides a and b of the outline fold back over each other; draw the outline again on the page (two neighbouring sides), or ... cross or touch; ... (any other two)
• NOT VALID: every opening needs an ID, a side, a start and a length
• NOT VALID: every gate needs an ID, a side, a start and a width
• NOT VALID: every opening ID is O and its number, written with at least three digits: O001, O002, O1000 (the number from 1 to 1,000,000,000)
• NOT VALID: every gate ID is G and its number, written with at least three digits: G001, G002, G1000
• NOT VALID: opening ID O001 is given to more than one row, and the same for a gate ID
• NOT VALID: opening O001's start or length is more than 83,333.33 ft (in Metric, 10,000 m), and the same for a gate's start or width
• NOT VALID: opening O001 is on side 5, but the outline has 4 sides; the side is a whole number from 1 to 4, and the same for a gate
• NOT VALID: opening O001 needs a length more than 0.00001 in (in Metric, 0.0000254 cm), and a gate a width more than that
• NOT VALID: opening O001 runs past an end of side 3, and the same for a gate
• NOT VALID: openings O001 and O002 overlap; openings may touch but not overlap
• NOT VALID: gate G001 is in opening O001: a gate goes on fence
• NOT VALID: gates G001 and G002 overlap
• NOT VALID: the openings leave no fence and no gate to count
• NOT VALID: post spacing must be greater than zero
• NOT VALID: choose a fence style
• NOT VALID: picket width must be greater than zero (Privacy and Picket fences)
• NOT VALID: enter a gap between pickets of 0 or more
• NOT VALID: enter a picket waste between 0% and 100%
• NOT VALID: rails per section must be a whole number, 0 or more
• NOT VALID: enter the widest gate hung as one leaf, more than zero
• NOT VALID: the fence height must be 2 to 12 ft (0.6 to 3.6 m)
• NOT VALID: the post depth must be 1 to 6 ft (0.3 to 1.8 m)
• NOT VALID: choose how the posts are set
• NOT VALID: choose a post size
• NOT VALID: a hole diameter, when entered, must be 4 to 36 in (10 to 90 cm); leave it blank for the typical concrete
• NOT VALID: the hole must be wider than the post's diagonal, 4.95 in (a 4x4; 7.78 in for a 6x6, 12.73 cm for a 90 mm post and 19.80 cm for a 140 mm post), with concrete chosen
• NOT VALID: choose a concrete bag size
• NOT VALID: choose a rail board length
• NOT VALID: choose whether to include post caps, and the same for a kickboard
• CHECK: side k has fence posts closer than 4 in; widen the post spacing, or make the items beside a short stretch of fence touch or leave room for a post
• CHECK: opening O001 is shorter than 4 in; check it on the drawing
• CHECK: gate G001 is narrower than 4 in; check it on the drawing
• CHECK: each post is 18.00 ft, longer than the longest stock post, 16.00 ft; order the posts to length (in Metric, metres)

Otherwise the status is OK. The first three CHECK: lines share one threshold, 4 in (10 cm), about a post's width: two posts closer than that cannot both stand. Between two neighbouring posts along the fence lies a stretch of fence, a gate or a run of openings (one opening, or several touching end to end), so any two posts closer than 4 in raise one of them: fence posts closer than 4 in on a stretch (a stretch shorter than 4 in; in the workbook itself, also a post spacing that cuts a stretch into sections under 4 in, which the platform's 1 ft minimum refuses first), an opening shorter than 4 in, or a gate narrower than 4 in. Under CHECK: every figure and the gate schedule are still shown; a NOT VALID: verdict is shown in place of them, every figure reading 0.

Every check this workbook makes applies to the web page, an API call and an MCP call alike; the platform first refuses out-of-bounds, mistyped and missing required values in its own words. A direct caller through the API or MCP sends the outline's points in order and the two tables, in the selected system's unit, and the spreadsheet refuses in its own words everything the drawing refuses (a malformed row, an overlap, an outline that crosses itself), so a caller without a drawing gets a NOT VALID: line, never a wrong figure.

Assumptions and limitations

• The fence height sets the post and picket lengths only: no count here depends on it. A tall fence's larger posts, closer post spacing or extra rails are your inputs, not derived from the height.
• The post depth is an input, not derived from the height, the frost depth or the soil; it sets the post length and the concrete, in proportion to a 2 ft (0.6 m) hole of the same width when no hole diameter is entered.
• A post stands at every point of the outline the fence or a gate reaches, a point on a straight side included: a point added to a straight side adds a post and a section.
• A gate's width is taken out of the fence: its rails, pickets, panels and kickboard are not counted, and the gate itself is hardware. A two-leaf gate's leaves are not limited in width: a very wide gate is still two leaves.
• The typical concrete a post (0.9 cu ft, 2 bags of 60 lb, for a hole 2 ft deep), the bag yields, the 2 hinges for each leaf, the latch for each gate, the drop rod for each two-leaf gate, the 2 fasteners for each picket on each rail and the 2 brackets for each rail are typical figures for review before use. A wider hole, a larger post or a frost footing takes more concrete, a manufacturer's bags-per-post table may run above a hole's net volume, and a tall or heavy leaf may need a third hinge. Gravel and soil for posts set without concrete are not counted.
• The stock lengths are common lumber lengths: posts from 8 to 16 ft (2.4 to 4.8 m) and rail boards in the four lengths offered. Rail and kickboard boards are counted without cutting waste, and a board never crosses a gate, an opening or a corner.
• Outline points, and an item's start, length or width, beyond 1,000,000 in (83,333.33 ft) or 1,000,000 cm (10,000 m) from the origin are refused, as FloorCanvas refuses them.
• The drawing holds 100 outline points, 20 openings and 20 gates.
• The Metric defaults are round figures, not conversions of the US ones.
• Worked examples 11.5.3.1, 11.5.3.2, 11.5.3.3 and 11.5.3.5 differ from the printed figures, because each gate's width is taken out of the fence and its posts are counted where they stand, never added to a count made along the fence: 11.5.3.1 keeps its 21 posts but has 19 sections, 57 rails and 286 pickets; 11.5.3.2 has 15 posts and 30 bags; and 11.5.3.3 and 11.5.3.5, drawn as the closed yards they describe, have 42 and 22 posts, 84 and 44 bags.
• Slopes, curves, frost depth, soil, wind load, pool-barrier, boundary and height rules, hardware sizes and prices are not modelled.

Restrictions and non-computing states

This calculator accepts a closed outline of 3 to 100 points that does not cross or touch itself, up to 20 openings and 20 gates on its sides, a fence height from 2 to 12 ft (0.6 to 3.6 m), a post spacing of at least 1 ft (0.3 m in Metric), a post depth from 1 to 6 ft (0.3 to 1.8 m), a hole diameter, when entered, from 4 to 36 in (10 to 90 cm), a picket width from 0.5 to 24 in (1 to 60 cm) and a gap from 0 to 24 in (0 to 60 cm) whatever the style, a widest single gate of zero or more, a whole number of rails per section from 0 to 10 and a picket waste from none to all, with the unit system US or Metric, the style Privacy, Picket, Panel or Rail and each choice one of its listed options. The platform refuses a value outside these bounds in its own words before it reaches the spreadsheet. The fields of the system that is not selected are not read. An outline that crosses or folds back over itself or repeats a point, a row that is incomplete, badly named, out of range, on no side, of no size, past its side's end or overlapping another item, openings that leave no fence and no gate, a widest single gate of zero, and a hole no wider than the post's diagonal are not computed; the workbook itself also refuses a post spacing or, for a privacy or picket fence, a picket width of zero, which the platform refuses first.

Errors and warnings

A blank required input keeps Calculate from sending, and pressing it names the input and moves to it; the hole diameter is optional and may stay blank. If the calculation service refuses an input, the status line names it. If the service does not answer, the page says so, keeps your drawing, your inputs and the last result, and lets you press Calculate again. A CHECK: status means the figures are returned with a reason to look again; a NOT VALID: status means they cannot be computed and none are shown.

Sources and further reading

• National Institute of Standards and Technology, Guide for the Use of the International System of Units (SI), NIST Special Publication 811, Appendix B.8. nist.gov. The exact inch (2.54 cm) and foot (0.3048 m), from which 12 inches make a foot, the figure the US picket count uses, a cubic foot is 28.316846592 litres, the figure the Metric bag yields use, and by which the Metric defaults are shown not to be conversions: 6 ft is 1.8288 m, not 1.8 m, 8 ft is 2.4384 m, not 2.4 m, 2 ft is 0.6096 m, not 0.6 m, 5.5 in is 13.97 cm, not 14 cm, and 4 ft is 1.2192 m, not 1.2 m.
• Your Fence Store, "How to Install Chain Link Fence." yourfencestore.com. Terminal posts are the end, corner and gate posts, and line posts stand between them, no more than 10 feet apart: the basis of counting each post by where it stands, with line posts at no more than the post spacing.
• Frederick Fence Co., "8 Tips for Building a Wood Fence Gate." frederickfence.com. A single wood gate no wider than four feet, and a double gate that meets in the middle for anything wider: the basis of the default widest gate hung as one leaf, 4 ft, and of the two leaves.
• Fence Advisors, "How to Build & Install a Fence Gate: Swing, Slide & Double Drive." fenceadvisors.com. The drop rod on one leaf of a double gate, which locks into a ground sleeve so the other leaf latches against it; two or three strap hinges and a latch to a gate: the basis of the drop rod on each two-leaf gate, the hinges for each leaf and the latch for each gate.
• Family Handyman, "How to Build a Fence Gate (DIY)." familyhandyman.com. Posts that flank gates demand extra care in plumbing and bracing, and a double gate is built narrower than its opening for clearance: why a gate's own posts are counted as gate posts, and why the gate's width here is its opening.
• The QUIKRETE Companies, Concrete Mix, Product No. 1101, data sheet (revised October 2022). quikrete.com. One manufacturer's yields for premixed concrete: about 0.30, 0.375, 0.45 and 0.60 cu ft from its 40, 50, 60 and 80 lb bags, the yields the bags are counted at, and a post hole about 3 times the post's width. Its own bags-per-post guidance may run above a hole's net volume, which this calculator counts without an allowance.
• American Softwood Lumber Standard (NIST PS 20), as stated by the Southern Pine Inspection Bureau: a dressed 4x4 is 3.5 in square and a 6x6 5.5 in square, the post widths the hole's net volume is counted with.
• Western Red Cedar Lumber Association, "Fence Specifications": dressed metric fence posts of 90 and 140 mm, the Metric post sizes.
• Natural Resources Canada, "Dimension lumber": lumber lengths in multiples of 2 ft (60 cm), the basis of the post and rail board stock lengths.
• Simpson Strong-Tie, "FB Fence Bracket": a bracket connects a rail to a post, the basis of the 2 brackets for each rail.

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The defaults (the fence height, the post spacing, size and depth, the post setting, the bag, the rail board length, the rails, the picket size and gap, the waste and the widest single gate), the typical concrete a post when no hole diameter is entered (0.9 cu ft, 2 bags of 60 lb, for a hole 2 ft deep), the 2 hinges for each leaf, the latch for each gate, the drop rod for each two-leaf gate, the 2 fasteners for each picket on each rail, the 2 brackets for each rail and the 4 in (10 cm) closeness threshold are typical figures, review before use; they are not values from these sources or from any code or standard, and each system has its own. These sources describe the units, the sizes and common practice; they do not certify a particular fence or its count. Use your supplier's post, rail, picket, panel, concrete and gate hardware sizes, check the layout and the site, and check the local rules for pool barriers, boundary fences, fence height and post footings before you order or build.