Compound Interest Calculator
See how savings or investments could grow with compound interest and regular monthly contributions, with a year-by-year breakdown.
- Total you paid in
- £0
- Interest earned
- £0
| Year | Paid in so far | Interest so far | Balance |
|---|
How it works
Each month the calculator adds interest at the monthly equivalent of your annual rate, then adds your contribution. The table shows how much of the balance is money you paid in and how much is growth.
Things to keep in mind
- Starting early matters more than the size of the monthly amount, because growth compounds on growth.
- Small differences in rate or fees add up over decades.
- Results are before tax, fees and inflation.
Free guidance is available from Money Helper.
Frequently asked questions
What is compound interest?
Compound interest is interest earned on both your original money and on the interest already added. Over long periods this makes balances grow faster than simple interest.
Is the rate AER or a nominal rate?
The calculator treats the rate as an effective annual rate (AER), which is how UK savings accounts advertise returns, and converts it to an equivalent monthly rate.
Does this include tax or inflation?
No. Interest above your Personal Savings Allowance may be taxable, and inflation reduces what the money buys. ISAs shelter interest from tax.
Can I use it for investments?
You can enter an assumed annual return, but investment returns are not guaranteed and vary year to year. Treat the result as an illustration, not a forecast.
These results are estimates for general information only and are not financial or tax advice. See our disclaimer.