Compound interest calculator
Calculate how savings grow with compound interest. Add regular contributions, choose compounding frequency and see projected growth charts.
- Free, no sign-up
- No data stored
- Reviewed 2026-01-15
Your details
Results
- Total invested
- £55,000.00
- Interest earned
- £32,959.28
- Growth multiple
- 1.60×
- Effective rate
- 5.12 %
- Real value
- £65,355.04
Real value (inflation-adjusted): :amount
- Balance
- Total invested
Yearly breakdown
| Year | Opening | Contributions | Interest | Closing |
|---|---|---|---|---|
| 1 | £10,000.00 | £3,000.00 | £581.33 | £13,581.33 |
| 2 | £13,581.33 | £3,000.00 | £764.56 | £17,345.89 |
| 3 | £17,345.89 | £3,000.00 | £957.16 | £21,303.06 |
| 4 | £21,303.06 | £3,000.00 | £1,159.62 | £25,462.67 |
| 5 | £25,462.67 | £3,000.00 | £1,372.43 | £29,835.11 |
| 6 | £29,835.11 | £3,000.00 | £1,596.13 | £34,431.24 |
| 7 | £34,431.24 | £3,000.00 | £1,831.28 | £39,262.52 |
| 8 | £39,262.52 | £3,000.00 | £2,078.46 | £44,340.98 |
| 9 | £44,340.98 | £3,000.00 | £2,338.28 | £49,679.27 |
| 10 | £49,679.27 | £3,000.00 | £2,611.40 | £55,290.66 |
| 11 | £55,290.66 | £3,000.00 | £2,898.49 | £61,189.15 |
| 12 | £61,189.15 | £3,000.00 | £3,200.27 | £67,389.42 |
| 13 | £67,389.42 | £3,000.00 | £3,517.48 | £73,906.91 |
| 14 | £73,906.91 | £3,000.00 | £3,850.93 | £80,757.84 |
| 15 | £80,757.84 | £3,000.00 | £4,201.44 | £87,959.28 |
About the Compound Interest Calculator
See how your savings or investments could grow over time with the power of compound interest. Enter a starting balance, monthly contribution, expected annual return and time horizon.
The calculator shows year-by-year growth including the effects of different compounding frequencies (monthly, quarterly, annually). An optional inflation adjustment shows the real purchasing power of your future balance.
How to use the Compound Interest Calculator
- Enter your starting balance.
- Add a monthly savings amount.
- Set the expected annual return rate.
- Choose the time period in years.
- Select compounding frequency and view the growth chart.
Formula and method
A = P(1 + r/n)nt + PMT × [((1 + r/n)nt − 1) / (r/n)] where P = principal, r = annual rate, n = compounds per year, t = years, PMT = periodic contribution.
Frequently asked questions
What compounding frequency should I use?
Most savings accounts compound daily or monthly. Investment returns are typically modelled annually. Monthly compounding is a good general default.
Does this account for tax?
No. Returns are shown before tax. Use a post-tax return rate for a more realistic estimate — for example, if returns are taxed at 20%, enter 80% of the expected rate.
What is the effect of inflation?
Tick the inflation option and enter an annual rate (e.g. 2.5%) to see your future balance in today's purchasing power.
How accurate are projections over 30+ years?
Longer time horizons are less certain. Real market returns fluctuate. Use the result as a guide for planning, not a guarantee.
Sources
Figures are estimates for guidance only. Always confirm with the official source or a qualified professional before acting on them.