Compound Interest Calculator UK
See how your money grows when you earn interest on your interest, with an optional monthly deposit.
Estimates for information only, using 2026/27 rates for England, Wales and Northern Ireland unless stated. Not financial or tax advice; check your own situation with HMRC or a qualified adviser.
How it works
Each period, interest is added to your balance, and next period's interest is earned on the new, bigger balance. That's compounding.
More frequent compounding (monthly rather than yearly) grows money slightly faster at the same rate.
The chart separates what you paid in from what interest added, so you can see compounding take over in later years.
Frequently asked questions
What's the rule of 72?+
Divide 72 by the interest rate to estimate how many years it takes to double your money. At 6%, about 12 years.
Is interest on savings taxed?+
Above your Personal Savings Allowance (Β£1,000 for basic-rate taxpayers, Β£500 for higher-rate). ISAs are tax-free.