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ToolBoxGenie

Savings Calculator

Calculators · Added 15 August 2026

One calculator answering the three savings questions people actually ask: what will I have, how much must I put aside, and how long will it take. All three are the same equation rearranged, so the answers always agree with one another — and deposit timing is an explicit choice rather than a hidden assumption.

What do you want to work out?

Leave at zero if you are starting from nothing

years
%

Compounded monthly

%

Shows the result in today's money

Deposits made at the

How to use the savings calculator

  1. 1Pick which of the three questions you want answered.
  2. 2Enter your starting balance, or leave it at zero if you are beginning from nothing.
  3. 3Fill in the monthly deposit, the goal, or the time frame depending on the mode.
  4. 4Set the annual return, and optionally an inflation rate to see the result in today's money.
  5. 5Choose whether deposits land at the start or end of each month — it changes the answer.

Examples

What will I have?

Input
£250 a month for 10 years at 5%
Result
£38,821 — £30,000 deposited, £8,821 earned

Deposits at the end of each month, the usual savings-account assumption.

What must I save?

Input
Goal £50,000 in 15 years, £5,000 already saved, 6% return
Result
£130.86 a month

The existing £5,000 grows on its own and reduces what you need to add.

Inflation-adjusted

Input
£1,000 a month for 25 years at 7%, inflation 3%
Result
£810,700 nominal · £387,200 in today's money

Inflation halves the purchasing power of a long-term result. This is why the option exists.

About the savings calculator

Three questions, one equation

Every savings question is the same relationship between five quantities: what you start with, what you add, the rate, the time, and what you end with. Fix any four and the fifth follows. That is why this calculator has three modes rather than three separate tools — solving for the final balance, the monthly deposit or the number of months are all rearrangements of one formula.

Keeping them together has a practical benefit beyond tidiness: the answers cannot disagree. Work out the monthly deposit needed for a goal, then feed that deposit back into the future-value mode, and it lands exactly on the goal. Separate implementations of the same maths tend to drift apart on rounding and on assumptions like deposit timing, which is how people end up with two calculators giving different answers to the same question.

The one genuinely different mode is time-to-goal, because time appears in an exponent and has to be solved with a logarithm rather than by rearranging. It is also the only one that can legitimately return no answer at all: if the deposits and growth are too small relative to the target, the goal is not reached in any timeframe worth reporting, and saying so is more useful than returning a number in the hundreds of years.

Why the early years feel so unrewarding

Compound growth is famously back-loaded, and the consequence is that a savings plan feels ineffective for a long time before it feels effective. In the first years, almost all of the balance is money you put in — the interest is a rounding error against the deposits. That is not a sign the plan is failing; it is what the arithmetic looks like at the start.

The crossover, where cumulative growth exceeds cumulative deposits, typically arrives somewhere between fifteen and twenty-five years in at ordinary rates. Before it, the deposits dominate; after it, the growth does, and increasingly so. The year-by-year table on this page makes the shift visible, and it is worth looking at when a plan feels pointless in year three.

The practical implication is that time in the plan matters more than the amount, up to a point. Starting ten years earlier with a smaller deposit frequently beats starting later with a larger one, because the early money has the longest to compound. This is unhelpful advice for anyone already past that point — but it is the honest reason that starting small and starting now is usually better than waiting until you can start properly.

What a smooth projection cannot tell you

This calculator, like every one of its kind, applies a constant return every month. Real savings rates move with central bank policy, and real investment returns vary wildly year to year — the average is an average of good and bad years, not a description of any of them.

That matters most for sequence risk, which a smooth projection cannot show at all. Two portfolios with identical average returns can end at very different places depending on when the bad years fall, particularly if money is being withdrawn. For a savings plan with regular deposits the effect is milder and can even work in your favour, since deposits made during a downturn buy in cheaply.

The right way to use a figure from a calculator like this is as a planning benchmark, not a forecast: it tells you whether a goal is roughly plausible on your current contributions, and how sensitive that is to the rate you assume. Change the rate by a point or two and see how much the answer moves — if the plan only works at an optimistic rate, that is the important output, not the headline number.

Frequently asked questions

Does it matter whether I save at the start or end of the month?
More than people expect over a long period. A deposit made at the start of the month earns a month's growth that an end-of-month deposit does not, so the same plan produces a slightly larger balance. Over thirty years at a reasonable rate that compounds into a difference of several percent. Most savings accounts credit interest on the balance held, so if your salary arrives and you transfer immediately, start-of-month is the accurate choice. Calculators that do not say which they use are the reason two of them disagree on identical inputs.
What return should I assume?
Whatever is genuinely available to you, and no more. A savings account pays whatever the current rate is, and it changes. Investments have historically returned more over long periods but with real volatility and no guarantee — a figure like 7% is a long-run historical average for equities, not a rate you receive each year, and some years are negative. Deliberately no default rate is suggested here, because a plausible-looking number in a calculator becomes an expectation, and this site does not give investment advice.
Why include inflation?
Because a large nominal number thirty years out is misleading on its own. If prices rise 3% a year, something costing £100 today costs about £243 in thirty years, so a £500,000 pot then buys what roughly £206,000 buys now. The inflation field discounts the result back to today's purchasing power, which is the figure that actually tells you whether the plan is enough.
Is tax accounted for?
No. Interest and investment gains may be taxable depending on your country, the account type and your circumstances — tax-sheltered accounts like an ISA, 401(k), PPF or equivalent change the picture substantially. The figures here are before any tax, so treat them as an upper bound unless the money is in a sheltered account.
How is this different from the compound interest calculator?
The compound interest calculator answers one question — what a balance grows to — and lets you vary the compounding frequency. This one solves in three directions, so it can tell you the monthly amount needed for a target or the time a goal will take, and it adds the deposit-timing choice and inflation adjustment. Use that one for the mechanics of compounding, this one for planning against a goal.

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