Compound interest calculator
Initial capital, monthly contribution, interest rate and years — see how your money grows, with a chart and year-by-year table.
| Year | Contributed | Interest | Balance |
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🔒 100% private — the calculation happens on your device, nothing is uploaded to any server.
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1. Enter your numbers
Initial capital, monthly contribution, interest and years.
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2. Check the result
Final balance, total contributed and interest earned, instantly.
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3. Check the growth
Year-by-year table with contributions, interest and balance.
How it works
Uses monthly compounding: each month, the balance earns interest proportional to the annual rate divided by 12, and that interest is added to the principal before the next month's interest is calculated — hence "compound interest." If you add a monthly contribution, it's also added each month, so it starts earning its own interest from the month it's contributed.
Why it doesn't include taxes
Capital gains taxation varies a lot by country, product (savings account, fund, stocks...) and your personal situation, so trying to calculate it would give wrong results for most people. This calculator shows gross growth — the part that's the same for anyone with the same input numbers.
Frequently asked questions
How is compound interest calculated here?
With monthly compounding: each month, the interest earned is added to the principal, and the next month's interest is calculated from there. If you add a monthly contribution, it's added to the principal each month before the next month's interest is calculated.
Is my data uploaded to a server?
No. All calculation happens in your browser. No data you enter is transmitted anywhere.
Does it include taxes on the gains?
No. Taxes on capital gains or investment returns vary a lot by country and financial product, so this calculator shows gross growth, before taxes.