Savings Goal Calculator

How unsure you are about that yearly return, as one standard deviation. It is as much a part of the answer as the return itself, which is why it is asked for rather than assumed: the model runs the plan across eleven returns and reports how often it arrives. Six percent is in the range of a mixed portfolio and fifteen is closer to all equities. Quote it per YEAR; it is scaled to your deadline by the square root of time, because one constant rate over many years is less uncertain than a single year. Zero says the return is settled, and the grid collapses onto your own figure.

Optional. What you actually intend to put aside each month, if that is not the figure the plan asks for. Leave it blank and the model runs on what the restated goal needs, so the surplus is exactly nothing by construction. Fill it in and the surplus says how far ahead or behind you land, and the chance beside it moves with you.

How long until you need the money. It is the single input the answer is most sensitive to, because growth has longer to work and the monthly figure falls faster than the years rise.

The sum you want to have on the day. Enter it in today's prices if you are also entering an inflation rate, because the model will restate it for you; enter the future price if you are not.

What you expect the money to earn each year, after fees and before tax. A cash savings account and a diversified fund are different assumptions and the answer changes by a third between them, so this is a judgment rather than a default.

What is set aside for this goal today. It keeps growing at the return you expect whether or not you add anything, so it reduces the monthly figure by more than its own size.

Optional. How fast the price of the thing you are saving for rises. Leave it blank to treat the goal as a fixed number of dollars. Fill it in and the goal is restated at the deadline, which over ten years at three percent raises the monthly figure by about a third: the commonest way a savings plan arrives on target and still cannot buy the thing.

Whether the money goes in at the end of each month or at the start. A standing order on payday is a start-of-month contribution and buys one extra month of growth on every payment, which is worth about half a percent of the monthly figure at five percent.

Where it lands in a lucky tenth. The distance between this and the unlucky tenth is the honest width of the answer, and on a long plan it is usually wider than the goal itself.

The values across the top of the grid: how long you might give yourself, in whole years either side of your deadline and never below one. Read a column to hold the deadline fixed. The middle entry is your own figure.

Where it lands in the middle of the weighted outcomes. It sits near the single-point answer rather than on top of it, because compounding is not symmetric in the return.

The balance less the restated goal. Positive means you arrive ahead, negative means short and by how much. Exactly nothing when you leave the planned contribution blank, because the model is then running on the contribution that lands on the goal. This is the figure the grid below sweeps, so its sign is what the colours mean.

Where the plan lands in an unlucky tenth of the returns: the shortfall you should be able to absorb, or plan around, rather than the one you expect.

Machinery, and NOT an input. The same for the column axis: Excel substitutes into it while filling the grid, and the rest of the time it mirrors Years_To_Goal.

The body of the grid: the surplus at the deadline, recomputed for every combination of the two axes. One hundred and twenty-one cells, each one the whole plan run again on the contribution you are actually making. It is a component of the table rather than a result on its own.

The monthly contribution times the number of months. Cash out of your pocket over the plan, not counting what was already saved.

Machinery, and NOT an input. Excel substitutes each value from the row axis into this cell while it fills the grid; the rest of the time it mirrors Annual_Return. Change Annual_Return above, never this: the axis is derived from it, so editing the mirror moves the axis while the table walks and the grid comes out meaningless.

Machinery. Excel requires the formula being tabulated to sit in the grid's top-left corner, where it means nothing to a reader, so it is formatted away. It holds Surplus_At_Deadline.

The values down the left of the grid: the average return you might actually get, spread around the one you expect. Read a row to hold the return fixed and vary the deadline. The middle entry is your own figure.

The level monthly amount that turns what you have into the goal as you stated it, at the return you expect. Zero when what you have already saved grows past the goal on its own.

The balance less everything that went into it. Over a long plan it is often larger than the contributions, which is the argument for starting early stated as a number rather than as advice.

The monthly amount the balance, the surplus and the grid are all computed from: what you entered, or what the restated goal needs if you entered nothing. It is held at this figure across the whole grid on purpose, so the grid asks what happens to YOUR plan rather than recomputing a new plan in every cell.

What the plan leaves you with on the day: what you had grown, plus every contribution grown from the month it went in.

The monthly amount that reaches the restated goal rather than the stated one. This is the honest figure when you are saving for a thing rather than for a number of dollars, and it is the one the rest of this page runs on unless you enter your own.

Growth as a share of the final balance. It rises steeply with the years and is the clearest single measure of how much of the work the return is doing rather than you.

The share of the returns in the grid, weighted by how likely each one is, in which the plan still arrives at or above the goal by your own deadline. At the contribution a calculator hands you it sits near a half, and that is the finding this tool exists for: the figure everyone quotes is the one that works at the average, and half of all futures are below average. It is a statement about the spread you entered and nothing else.

What is already set aside, grown to the deadline on its own with nothing added. The rest of the goal is what the monthly contributions have to cover.

Reads OK, or explains why the inputs are not valid or why the answer deserves a second look.

The goal compounded to the deadline at the inflation rate you entered. It is the same goal in later money, and it is what the plan actually has to reach. Equal to the goal when no inflation is entered.

The gap between the two monthly figures, which is what rising prices add to the plan. Zero when no inflation is entered. It compounds with the years, so it is small over three and substantial over twenty.