UK Interest Calculator
Use this interest calculator to estimate how your savings could grow over time with compound interest, regular contributions, and different interest rates.
Estimated balance
£0
Based on starting savings, contributions, rate, and time
Compound growth estimate
Total interest earned
£0
Total contributions
£0
Starting amount
£0
Time period
0 years
| Year | Contributions | Interest earned | Closing balance |
|---|
Assumptions
Estimates assume a fixed interest rate over the full period and do not include tax, fees, inflation, or future rate changes.
Compound interest is interest earned on both your original savings and on the interest you have already earned. Each period, the interest is added to your balance, and the next period's interest is calculated on the new, larger total. Over time this compounding effect becomes the main driver of growth.
The longer you save and the higher the rate, the bigger the compounding effect. That's why starting early - even with small amounts - is usually more powerful than saving larger amounts later.
Simple interest pays a fixed amount based only on your original deposit, so £1,000 at 5% would always earn £50 a year, regardless of how long it's held. Compound interest earns interest on that interest too, so after a few years the balance grows faster than simple interest would suggest.
Most UK savings accounts and cash ISAs use some form of compounding, usually paying interest monthly or annually into the same account.
Adding money regularly grows your balance in two ways: each contribution adds directly to the total, and each contribution starts earning its own interest from the moment it's deposited. The earlier a contribution is added, the more time it has to compound.
Even modest monthly amounts can make a substantial difference over a decade or more. Try changing the regular contribution in the calculator to see how much of your final balance comes from contributions versus interest.
Compound frequency is how often interest is added to your balance. Daily compounding adds interest 365 times a year, weekly 52, monthly 12, and yearly once. At the same quoted annual rate, more frequent compounding produces a slightly higher final balance because the interest starts earning its own interest sooner.
The gap between yearly and monthly compounding is usually the most visible; moving from monthly to weekly or daily makes a smaller additional difference. The calculator lets you switch between all four under Advanced options.
This calculator uses a fixed interest rate for the full period. It does not account for tax on savings interest, the Personal Savings Allowance, ISA allowances, inflation, or future rate changes. Results are estimates to help compare scenarios, not a guaranteed return.
The interest you earn depends on your starting amount, how much you add over time, the interest rate, and how long you save for. This calculator projects a final balance by simulating your savings month by month using compound interest.
Compound interest means you earn interest on your original savings and on the interest you've already earned. Over long periods this compounding effect can significantly boost the final balance compared with simple interest.
Yes. Regular monthly contributions steadily increase the balance earning interest, so small amounts added consistently can make a meaningful difference over several years - especially at higher interest rates.
This calculator gives an estimate using a fixed interest rate and the compound frequency you choose. Real-world savings accounts may have variable rates, fees, or bonus periods, so your actual return can differ. Use this as a guide rather than a guarantee.
No. This version does not include UK savings tax, the Personal Savings Allowance, or ISA rules. For tax-free saving, consider whether an ISA is suitable for your situation.
How much you can save each month depends on your income and outgoings. Use our other free calculators to see the full picture. If you are weighing pension saving against cash saving, the pension tax relief calculator helps show the tax side. If you want a tax-free wrapper view with ISA allowance checks, try the Cash ISA calculator. If you are saving for a first-home deposit, a Lifetime ISA can also change the numbers by adding a government bonus. Saving for a child instead? The Junior ISA calculator is a useful companion. If debt repayment is competing with saving, compare the numbers with our Debt Payoff Calculator. You can also pressure-test future buying power assumptions with our Inflation Impact Calculator.
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