Compound interest calculator
Work out how your money grows with an initial amount, regular contributions, inflation and taxes, with a chart and a year-by-year table.
Final value
Total contributed
Interest earned
Taxes and fees
Real value (after inflation)
Effective annual rate
Total withdrawn
Year-by-year growth
Compare scenarios
Keep up to 3 calculations side by side: change the figures and add another.
There are already 3 scenarios: remove one to add another.
Calculation breakdown
Enter a duration to see the breakdown.
Report with the result
The report includes the summary, the simulation inputs, the chart and the year-by-year breakdown.
This is an estimate based on the figures you enter, not financial advice: actual returns may vary and taxes depend on your country and situation.
How to calculate compound interest
With compound interest, the interest is added to the capital and earns interest in turn. The calculator simulates every contribution, withdrawal, tax and fee on its date and shows the result year by year, all inside your browser.
Enter the initial amount, the interest rate (nominal or effective), the compounding and the duration.
Optionally add regular contributions or withdrawals, inflation, taxes, fees and rate changes by year.
Check the chart and table, compare up to 3 scenarios, download the breakdown as CSV or Excel, or copy the link to share the calculation.
Why use JapalTools?
Your files never leave your device
Everything happens in your browser. Documents are never uploaded to any server, so you can use it with payslips, contracts or ID documents.
Free, no sign-up and no watermarks
You don't need an account or to leave your email, and nothing is added to the result.
Works on any device
Computer, tablet or phone, with an up-to-date browser (Chrome, Edge, Firefox or Safari). Nothing to install.
Frequently asked questions
The nominal rate (APR) does not include compounding: 5% compounded monthly actually yields 5.12% a year. The effective rate (APY) already includes it, so with it the compounding frequency does not change the result. The calculator always shows you the effective annual rate.
The equivalent rate is used: each amount grows at the effective annual rate for the exact time it is invested. If you contribute at the start of the period, that contribution earns one more period of interest than at the end.
The management fee is deducted gradually from the balance, as in a fund. Tax is paid every year on that year’s gain (losses are offset against later gains) or once at the end on the total gain. This is a simplification: real taxation depends on your country.
You enter the amount you want to reach and the calculator searches, by repeating the simulation, for the time (up to 100 years, in months), the regular contribution or the interest rate needed with the rest of your figures. Rate changes by year are not used when solving for the rate.
They are not stored on any server or in the browser. The figures are written into the page address itself (after the #), so you can bookmark it or share the link, and whoever opens it will see the same calculation and scenarios.
No. The document is processed in your own browser and is not sent to JapalTools or anyone else. When you close the page, no copy remains outside your device.