Window Replacement Calculator

Purpose and model boundary

This calculator prices replacement windows from a floor plan you draw. You draw the plan, add each window on an outer wall, and give each window a type. A window is either a standard window, one of the common standard sizes of its type (typical rough openings), or a custom window drawn to any width. The page lists one price row for each window type and size. You type a unit price on every row and, if you want it in the total, an installation price for each window. The spreadsheet counts the windows of each row and returns the cost of the windows, the installation, the total and the average per window, with a window schedule of every row.

The calculator multiplies the spreadsheet's count by the prices you type. It does not quote prices, and no price comes from any source. Prices are plain numbers in your currency, with two decimals and no currency sign. It is not a quote, a bid, a window order or a size check.

Not included:

• removing and disposing of the old windows;
• interior trim and casing, exterior trim, paint and finishing;
• flashing, sealant, foam, shims and other installation materials;
• labor beyond the installation price you enter;
• structural work: resizing an opening, new headers, repairing rot;
• permits, inspections and lead-safe work rules for older homes;
• delivery, sales tax and disposal fees;
• glass, grille, color, hardware and energy-rating options (put them in your unit price);
• doors, patio doors, skylights, bay and bow windows, composite, twin and shaped units;
• window coverings;
• ordering sizes. The sizes listed are typical rough openings. Replacement windows are usually made to the measured existing frame.

Inputs and units

The drawing is the first input. It writes the outline, one row per room, one row per wall side, one row per window and one row per door. Each window row has its ID, its width and the room it is in. The drawing also writes one row per window with its type and, for a standard window, its size code and its height in inches. The rooms, the walls, the doors and the wall height are written with every floor plan, but no price reads them.

To add a window, double-click an outer wall and choose Add window. On a US drawing you then choose Standard or Custom.

• Standard asks for the type, the size and the height from the floor. The size list holds the common standard sizes of that type, typical rough openings, each shown as width × height in inches, such as 36 × 48 in, with its code in the option's tooltip. The window is fitted on the wall where you double-clicked. It keeps its width when you move it. Dragging one of its ends changes its width and makes it a custom window.
• Custom is drawn along the wall to any width and then given a type. Type its height in the Windows table.

The six types are Double-hung, Single-hung, Sliding, Casement, Picture and Awning. The 4-digit code is the opening in feet and inches: 3040 is 3 ft 0 in by 4 ft 0 in, 36 × 48 in, and 5040 is 60 × 48 in. Standard sizes are offered on US drawings only. A Metric drawing has custom windows only, and switching a drawing to Metric makes every standard window custom, keeping its type; the drawing says so, and Undo restores both.

The Windows table holds each window's Height and Sill height, the height from the floor, in feet (US) or meters (Metric), never inches. A standard window's height is set by its size and shown read-only. A window's height must be 1 to 20 ft (0.30 to 6.00 m), and its height from the floor 0 to 20 ft (0 to 6.00 m). On the page the drawing asks for a window at least 1 ft (0.3048 m) and a door at least 5 ft (1.524 m) tall in both systems, so in Metric it refuses a 0.30 m window or a 1.50 m door that the spreadsheet alone would take. The height from the floor is checked and kept with the drawing, but it changes no price. Double-clicking a window on the drawing also sets its sill height and, for a custom window, its width and height. For a window with no sill yet, the pop-up offers one that puts the top of the window at 6 ft 8 in (2.03 m), at least 24 in (0.60 m) from the floor and within the wall height. A sill you type is kept.

The 3D button shows the drawing in 3D. After Calculate, each window is drawn by its type: the sashes of a double-hung, single-hung or sliding window, the hinge lines of a casement or awning window, the single pane of a picture window. The windows are drawn only while the result is up to date and its window schedule counts every window on the drawing; otherwise the view says why. The Wall height button sets the height of the walls for the 3D view, and every window must fit under it. The 3D view is a schematic: it changes no figure.

The price list has one row for each window type and size on the drawing. The page builds the rows: Type, Size (blank for a custom window), Width and Height, in inches (US) or centimeters (Metric). You type only the prices:

• Unit price: the price of one window of that row, 0 or more, required on every row.
• Installation, each: the price to install one window of that row, 0 or more. It may be left blank.

A row's width is the drawn width × 12 (US) or × 100 (Metric), rounded to four decimals. Its height is the size's height for a standard window, otherwise the typed height × 12 or × 100, rounded the same way. The rows come in a fixed order: the types in the order above, standard rows before custom rows, then by width, then by height. The prices you type stay with their type and size: a row that disappears when you delete its last window comes back with its prices on Undo.

The page opens on a 20 by 15 ft room with one custom double-hung window, 54 in wide and 48 in high, 2.67 ft from the floor, priced at 520.00 with no installation price. The total is 520.00.

Governing relationships

Each window is matched to a price row by four values: its type, its size, its width and its height. A window counts on a row only when all four are equal to the row's. The type and the size are compared exactly, capital letters included. The width and the height are compared after rounding to four decimals.

So two windows of the same size but different types are on two rows. A custom window of exactly a standard size is made to order, so it gets its own row, apart from the standard windows of that size. To price it with them, add it as a standard window.

For each price row:

Count = the number of windows whose type, size, width and height equal the row's

Windows = count × unit price

Installation = count × installation price, where a blank installation price counts as 0

Line total = windows + installation

Over the whole price list:

Windows = the sum of the rows' windows

Installation = the sum of the rows' installation

Total = windows + installation

Average per window = total ÷ windows drawn, and 0 when no window is drawn

Nothing is rounded except the lengths. The average is held unrounded and shown to two decimals.

Calculation sequence

1. The spreadsheet reads the unit system, the windows, each window's type and size, and the price list.
2. It checks them in the order of the status list below.
3. For each window it works out the width and height in inches or centimeters, and its key: type, size, width and height.
4. For each price row it counts the windows with the same key, and checks that every window has exactly one row and every row a window.
5. It multiplies each row's count by its prices and adds up the rows, the total and the average.
6. It chooses the status. When it begins NOT VALID:, every figure reads 0 and the schedule is blank.

The default works through as follows: one row, count 1; windows 1 × 520.00 = 520.00; installation 0.00; total 520.00; average 520.00 ÷ 1 = 520.00.

The worked examples are each checkable by hand. Their prices are illustrations, not quotes.

• Example 1, one bedroom. A 12 by 11 ft room with two standard double-hung windows, size 3040, at 420.00 each plus 150.00 each to install. One row, count 2. Windows 2 × 420.00 = 840.00, installation 2 × 150.00 = 300.00, total 1,140.00, average 1,140.00 ÷ 2 = 570.00.
• Example 2, a whole floor with three types. A 40 by 28 ft floor with four standard double-hung 3040 at 385.00, two standard sliding 5040 (60 × 48 in) at 510.00 and one standard picture 6040 (72 × 48 in) at 640.00, each installed for 175.00. Three rows, counts 4, 2 and 1. Windows 1,540.00 + 1,020.00 + 640.00 = 3,200.00, installation 7 × 175.00 = 1,225.00, total 4,425.00, average 4,425.00 ÷ 7 = 632.142857…, shown as 632.14.
• Example 3, one size and two types. A 16 by 14 ft room with two standard double-hung 3040 at 420.00 and two standard single-hung 3040 at 310.00, with no installation price. Two rows, because the types differ. Windows 840.00 + 620.00 = 1,460.00, installation 0.00, total 1,460.00, average 365.00. The status is OK: every installation price is blank, so the CHECK for installation priced on some rows only does not apply.
• Example 4, standard and custom of one type. A 36 by 30 ft floor with three standard double-hung 3040 at 385.00 plus 150.00, and two custom double-hung windows drawn 54 in wide with a 4 ft height, at 520.00 plus 225.00. 54 in is not a common standard width for a double-hung window. Two rows. Windows 1,155.00 + 1,040.00 = 2,195.00, installation 450.00 + 450.00 = 900.00, total 3,095.00, average 619.00.
• Example 5, a Metric drawing. A 5.0 by 4.0 m room with three custom casement windows 60 × 120 cm at 450.00 and one custom picture window 150 × 120 cm at 800.00, each installed for 120.00. Two rows, custom only. Windows 1,350.00 + 800.00 = 2,150.00, installation 4 × 120.00 = 480.00, total 2,630.00, average 657.50.

Outputs and interpretation

• Cost: the Total, the Windows (the cost of the windows themselves), the Installation and the Average per window, in your currency.
• Windows: Windows drawn, the number of windows on the drawing, and Window types and sizes, the number of price rows.
• Window schedule: one row for each price row, in the price list's order, with its type, size, width and height, the spreadsheet's count, the unit and installation prices, and the row's windows, installation and line total. Its columns add up to the cost figures.
• From the drawing: the floor area inside the outline, in sq ft or m². It is shown for reference; no price uses it.

The Count beside each price row on the page is the spreadsheet's count, taken from the window schedule. The page never counts. The Count is blank before the first Calculate and while the result is out of date.

The total covers the windows and the installation prices you entered, and nothing else. A blank installation price adds nothing. The height from the floor, the wall height, the rooms and the doors change no figure.

Validation and status logic

The status is the spreadsheet's own verdict. It is the first of these that applies:

• NOT VALID: The unit system must be US or Metric.
• NOT VALID: every outline point needs both coordinates
• NOT VALID: every point of exclusion 1 needs both coordinates (and likewise for exclusions 2 to 5). The drawing never sends half a point; a direct caller can.
• NOT VALID: outline and exclusion points must fill consecutive rows, with no blank row between them
• NOT VALID: Every window needs a type: double-click it on the drawing to choose one. A window has no type, for example on a drawing saved before window types existed.
• NOT VALID: A window type must be Double-hung, Single-hung, Sliding, Casement, Picture or Awning. A type is not one of the six, written exactly, capital letters included.
• NOT VALID: Enter the height of every custom window in the Windows table.
• NOT VALID: A standard window's width must match its size: add it again, or drag its end to make it custom. A standard window's width differs from its size's by more than 0.000001 in, or a standard size is sent on a Metric drawing.
• NOT VALID: Window heights must be 1 to 20 ft (0.30 to 6.00 m) and heights from the floor 0 to 20 ft (0 to 6.00 m).
• NOT VALID: Each window type and size needs exactly one row in the price list, and each row a window on the drawing. A window has no row, a row has no window, or a row is repeated.
• NOT VALID: Enter a unit price of 0 or more for every window size.
• NOT VALID: Installation prices must be 0 or more, or left blank.
• CHECK: No windows are drawn: double-click an outer wall and choose Add window.
• CHECK: Installation is priced for some window sizes only; the total leaves out the others. Some rows have an installation price and others are blank.
• OK when none of these applies.

Under CHECK: every figure and the schedule are still shown. A blank installation price counts as 0, so with the partly priced CHECK the total leaves out installation for the blank rows: in example 2 with the picture row's installation left blank, installation is 1,050.00, the total 4,250.00 and the average 607.14. A price of 0 is a price: 0 on every row reads OK, and so does blank on every row.

A NOT VALID: verdict is shown in place of the figures: every figure reads 0 and the schedule is blank. A wrong price list is refused, never priced, so a caller who sends the tables directly with a missing, extra or repeated row gets the NOT VALID: line, not a wrong total.

Assumptions and limitations

• The sizes are typical rough openings, the opening in the wall. A window unit is usually 1/2 in smaller each way. Replacement windows are usually made to the measured existing frame, so measure before you order.
• A common standard size is listed when both of the size charts cited under References list it for that type. Other sizes are drawn as custom windows.
• Standard sizes are for US drawings only. Metric drawings have custom windows only.
• A custom window of a standard size is priced on its own row.
• Every window on one row has the same unit price and the same installation price.
• Prices are your own. The calculator holds no prices.
• Doors, the rooms, the walls and the wall height are drawn with the plan but are not priced.

Restrictions and non-computing states

The drawing holds up to 50 windows, and the price list up to 50 rows. Each window needs a type, and each custom window a height. Window heights run from 1 to 20 ft (0.30 to 6.00 m) and heights from the floor from 0 to 20 ft (0 to 6.00 m). Prices are 0 or more; the unit price is required on every row, and the installation price may be blank. The unit system is US or Metric, and standard sizes are accepted on US drawings only.

The platform refuses a request with no window, a blank type, a blank height or height from the floor, a blank unit price or a negative price in its own words before it reaches the spreadsheet. The spreadsheet's own checks for these states guard a direct caller, and the page normally never reaches them.

Errors and warnings

A blank required input keeps Calculate from sending, and pressing it names the input and moves to it. 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.

A standard size that does not fit the free stretch of a wall is refused on the drawing, which says how much wall is left. Pick a smaller size, use another wall, or draw a custom window.

Sources and further reading

• Andersen Corporation, 100 Series standard size charts (2024-25 100 Series Product Guide): Double-Hung Windows Standard Size Chart, Single-Hung Windows Standard Size Chart, Gliding Windows: XO/OX Standard Size Chart, Casement Windows Standard Size Chart, Awning Windows Standard Size Chart and Picture Transom Windows Standard Size Chart. Listed at andersenwindows.com. Accessed 2026-11-02. One of the two sources of the common standard sizes, for double-hung, single-hung, sliding (XO/OX), casement, awning and picture windows. The 4-digit code is the opening in feet and inches: 3050 is 3 ft 0 in by 5 ft 0 in, 36 × 60 in. The charts pair each window dimension with a rough opening 1/2 in larger each way, for nail-fin (flange) frames.
• Pella Corporation, 2026 Architectural Design Manual, 250 Series chapters: Double-Hung, Single-Hung, Sliding Window, Casement, Awning and Fixed. Accessed 2026-11-02. The other source of the common standard sizes, from each chapter's table of single units; the Fixed chapter gives the picture windows. Its nominal sizes, written 3-0/5-0, are the same openings in feet and inches.
• Pella Corporation, 2026 Architectural Design Manual, Installation & Applications, "Rough Opening Sizes and Sealants." media.pella.com. Accessed 2026-11-02. Cited for the rough-opening convention only, not for sizes: rough opening = nominal size; the unit is 1/2 in smaller each way.
• 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 foot, 12 in, and meter, 100 cm: the factors that turn a drawn width in feet or meters into the price list's inches or centimeters.

A size is listed when both charts list it for that type: the same rough opening, width by height, is a standard single-unit size in both the 100 Series chart and the 250 Series chart. Picture windows under 24 in high are left out, as transom proportions. Composite, twin, bay and bow, transom and shaped units are not listed. The two publishers give the same rough opening for every listed size. Both treat the rough opening as a minimum that wraps and flashing may need to enlarge. No retailer's list was used.

These are new-construction sizes. Replacement windows are usually made to the measured existing frame, so the sizes listed are typical rough openings, not order sizes. Standard sizes are US sizes in inches; the charts' millimeter figures are not carried, so a Metric drawing has custom windows only.

Links were current at build time. If one moves, search the document's title rather than reporting a broken link as a defect.

No price comes from these sources or from any other: every price is the one you enter. These sources give sizes and units; they do not certify any window, size, count or price. The names are trademarks of their owners, and neither publisher endorses this calculator or has reviewed it. Measure the existing openings and confirm sizes and prices with your supplier and installer before you order.