Compound interest calculator
See how money grows when interest earns interest. Enter a starting amount, an optional monthly deposit, a rate and a number of years, and we show the final balance, how much of it is interest, and the whole working, year by year. It works for savings accounts and investments alike.
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The lump sum you are putting in today. Leave at 0 if you are starting from nothing and only saving monthly.
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How much you add every month. Leave at 0 to see just the starting amount grow. We assume it goes in at the start of each month, so it starts earning straight away.
Before any tax.
Up to 60.
What rate should I use?
For a savings account, use its interest rate. For investments, use the average yearly return you expect after fees; many people use 4% to 6% for a long-term mix of shares and bonds, but returns go up and down and are not guaranteed. The calculator ignores tax, so the result is before any tax you might owe.
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The more often interest is added, the sooner it starts earning interest of its own. Banks show the effect as the AER (annual equivalent rate): the rate you effectively earn over a year once compounding is included. Check the account details for how often yours is paid.
Tailor it to you: rising deposits, inflation
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How much your monthly deposit goes up each year. By a percentage: for example 3% to keep pace with pay rises, so £200 a month becomes £206 the next year. By a fixed amount: for example £25, so £200 a month becomes £225, then £250. Leave at 0 to keep it the same.
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Prices rise over time, so £1 in ten years buys less than £1 today. We divide the final balance by the growth in prices to show what it is worth in today's terms. 2% is the Bank of England's long-term target. Enter 0 to switch this off.
- Deposits go in at the start of each month. Interest is added at the frequency you choose: daily, monthly, or once a year. With once a year, interest builds up on the balance through the year and is paid in at the year end.
- The rate stays the same for the whole period. Real savings rates and investment returns change from year to year.
- No tax is deducted. In reality, savings interest above your Personal Savings Allowance is taxed; investment gains and dividends above their allowances are taxed unless held in an ISA or pension; and money taken out of a pension is taxed as income, apart from the 25% tax-free part.
- Figures are worked to the penny: each amount is rounded to the nearest penny as it is calculated, and every later figure is built from those amounts, so every line adds up exactly. HMRC's own systems may round some figures down to whole pounds, which can differ by a few pence. Illustrative, not financial advice.
After 10 years
Your final balance
from £10,000.00 paid in, at 4.5% a year (4.59% AER)
- Starting amount
- £10,000.00
- Total monthly deposits
- £0.00
- Interest earned
- £5,669.87
- Final balance
- £15,669.87
- Worth in today's money (2% inflation a year)
- £12,854.75
How it grows
Show the workings
| Year | Paid in | Interest | Balance |
|---|---|---|---|
| 1 | £0.00 | £459.40 | £10,459.40 |
| 2 | £0.00 | £480.49 | £10,939.89 |
| 3 | £0.00 | £502.57 | £11,442.46 |
| 4 | £0.00 | £525.66 | £11,968.12 |
| 5 | £0.00 | £549.82 | £12,517.94 |
| 6 | £0.00 | £575.08 | £13,093.02 |
| 7 | £0.00 | £601.48 | £13,694.50 |
| 8 | £0.00 | £629.11 | £14,323.61 |
| 9 | £0.00 | £658.01 | £14,981.62 |
| 10 | £0.00 | £688.25 | £15,669.87 |
Calculated at sjecapital.co.uk/compound-interest-calculator. Illustrative, not financial advice. SJE Capital Limited, company no. 15837169.