UK savings and compound interest calculator
See how your savings could grow with interest on interest. Add what you have now, what you will save each month, and the interest rate.
Your savings
Enter an interest rate and number of years to see the result.
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| Added | Interest | Balance |
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How compound interest works
With compound interest you earn interest on your original savings and also on the interest you have already earned. In the early years the effect is small, but it builds over time, so the longer you leave your money, the faster it grows.
This calculator adds interest to your balance every month and then adds your monthly deposit. The rate you enter is the annual rate, known as the AER, which already allows for compounding.
Regular saving
Adding a little every month often matters more than the starting amount. Each deposit starts earning interest as soon as it goes in. Try changing the monthly figure and the number of years to see which makes the bigger difference to you.
Tax on savings interest
Most people can earn some savings interest tax free. The Personal Savings Allowance is £1,000 a year for basic-rate taxpayers and £500 for higher-rate taxpayers, and additional-rate taxpayers do not get one. Interest earned inside an ISA is tax free and does not use up that allowance. You can put up to £20,000 a year into ISAs. See GOV.UK on tax-free interest on savings and GOV.UK on ISAs.
Inflation
Prices usually rise over time, so the same amount of money buys less in the future. If you add an inflation figure, the calculator also shows what your final balance would be worth in today's money, which gives a more realistic picture of your savings.
What this calculator assumes
- The interest rate stays the same for the whole period. Real savings rates change, especially on easy-access accounts.
- Deposits are made at the end of each month, and interest is added monthly.
- No tax is taken off, and no fees or withdrawals are included.
- Inflation, if you enter it, is a steady yearly rate.
- The result is an estimate, not a guarantee of what any account will pay.
Questions people ask
How much will £100 a month grow to?
It depends on the interest rate and how long you save. Enter 0 as your starting amount, £100 a month and a rate, then change the number of years to see how the balance grows. The longer you save, the more of the final balance comes from interest.
What is the difference between AER and gross rate?
The gross rate is the interest rate before compounding. AER, the annual equivalent rate, includes the effect of interest being added more than once a year, so it is the best figure for comparing accounts. Use the AER in this calculator.
Is my interest taxed?
Interest in a cash ISA is tax free. Outside an ISA, you can earn up to your Personal Savings Allowance before paying tax. This calculator shows interest before any tax.
Is what I type stored or shared?
No. The calculation runs in your browser and nothing you enter is sent to us. Our privacy page has the details.
Is this financial advice?
No. It gives an estimate for information only. For advice on saving or investing, speak to a regulated financial adviser.