← All Calculators
Compound Interest Calculator
See how your savings or investments grow over time with compound interest.
📖 What is compound interest?
Compound interest means you earn interest on your interest — your returns are reinvested, so your money grows exponentially over time. The longer you invest, the more dramatic the effect. Starting early makes a massive difference.
Example: £5,000 at 7%/yr for 30 years grows to ~£38,000 without adding a penny. Add £200/mo and it becomes ~£260,000.
£
£
0.5%Cash ISA ~4%Stocks ~7%20%
Final Balance
£124,379
Total Contributed
£53,000
Interest Earned
£71,379
💡 Investment Tips
✅ Start early — with these numbers, starting 10 years later would leave you with £44,665 instead of £124,379 — that's £79,714 less due to compound growth.
🏦 Use a Stocks & Shares ISA — all growth is completely tax free. £20,000/year allowance.
💡 The UK stock market has historically returned ~7% annually (including dividends). Use this as a benchmark.
💡 Even increasing your monthly contribution by £50 can add tens of thousands over 20+ years.
📈 Growth over time
Stacked: initial amount · monthly contributions · interest earned
Sources & References
Returns shown are illustrative. Past performance is not a guide to future returns.