Compound Interest Calculator — See Your Savings Grow
Project savings growth with regular contributions and any compounding frequency.
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| Year | Deposited | Interest | Balance |
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See what a starting balance plus regular contributions could grow into. Adjust the return, the contribution schedule and the compounding frequency, and watch the year-by-year breakdown update — including what the total is actually worth after inflation.
How to use Compound Interest Calculator
- Enter your starting amount and any regular contribution.
- Set the expected annual return and how long you will invest.
- Choose the compounding frequency.
- Read the year-by-year table to see when interest starts outgrowing your own deposits.
The point at which growth takes over
The interesting number in the table below the chart is the year your accumulated interest passes what you have deposited. With regular contributions at a 7% return that typically happens somewhere around year 15 to 18. Everything after that point is the compounding doing more work than you are — which is the entire argument for starting early rather than contributing more later.
Compounding frequency matters less than people think
Moving from annual to monthly compounding at 7% adds roughly 0.23 percentage points of effective annual return. Going from monthly to daily adds about 0.01 more. Frequency is a rounding error next to the rate itself and how long you stay invested.
Why the inflation figure is there
A balance of £500,000 in 30 years will not buy what £500,000 buys today. The "after inflation" tile shows the result in today's purchasing power at a 2.5% assumption, which is roughly the long-run target of most central banks. It is usually a sobering number, and it is the honest one.
About the return figure
This is a projection from a fixed rate, not a prediction. Real markets do not deliver a smooth 7% — they deliver +20% one year and −15% the next, and the order of those returns matters a great deal if you are drawing money out. Treat the output as an illustration of how compounding behaves, not as a forecast of your balance.
Frequently asked questions
What return rate should I use?
That is your judgement to make. For context, global stock markets have averaged roughly 7% a year after inflation over the long run, but with severe year-to-year swings. Savings accounts return far less. This is a projection tool, not a forecast.
How much does compounding frequency matter?
Less than people expect. At 7%, moving from annual to monthly compounding adds about 0.23 percentage points of effective return; monthly to daily adds roughly 0.01 more. The rate and the time invested matter far more.
Why show an inflation-adjusted figure?
Because a large number decades away buys less than it appears to. The adjusted tile shows the result in today's purchasing power at 2.5% inflation, which is roughly the long-run central bank target.
Does this account for tax?
No. Returns in a taxable account are reduced by tax on interest, dividends and gains, which varies by country and account type. Tax-sheltered accounts are closer to the untaxed figures shown here.