Category: Calculators
Compound Interest Calculator
Project savings with regular contributions
Enter a starting amount, an annual rate, a term and an optional regular contribution, then read the final balance, what you paid in and what the interest added, with a year-by-year table. Calculated in your browser.
| Year | Total paid in | Interest earned | Balance |
|---|---|---|---|
| 1 | 11,200.00 | 539.50 | 11,739.50 |
| 2 | 12,400.00 | 1,168.01 | 13,568.01 |
| 3 | 13,600.00 | 1,890.06 | 15,490.06 |
| 4 | 14,800.00 | 2,710.44 | 17,510.44 |
| 5 | 16,000.00 | 3,634.20 | 19,634.20 |
| 6 | 17,200.00 | 4,666.60 | 21,866.60 |
| 7 | 18,400.00 | 5,813.23 | 24,213.23 |
| 8 | 19,600.00 | 7,079.91 | 26,679.91 |
| 9 | 20,800.00 | 8,472.79 | 29,272.79 |
| 10 | 22,000.00 | 9,998.32 | 31,998.32 |
This is arithmetic on the numbers you typed, not financial advice, and it ignores tax, fees and inflation. Contributions are added at the end of each period.
Everything on this page is processed in your browser. Nothing is uploaded.
What this tool does
Compound interest is easy to state and awkward to compute once deposits are involved, because the deposits and the compounding rarely land on the same schedule. This tool steps through the whole term event by event: interest is credited only at a real compounding date, a deposit lands only on a real contribution date, and the balance carries forward. That is why monthly deposits with quarterly compounding give a different answer here than a single formula would. The table underneath shows each year separately, so you can see the point where the interest starts outgrowing what you pay in.
How to use it
- Enter the starting amount, the annual rate and how many years to run.
- Choose how often interest compounds, and add a regular contribution if you make one.
- Read the final balance, the interest earned and the year-by-year projection.
Privacy
This tool runs entirely in your browser. Your input is never uploaded, stored or shared — closing the tab removes it.
Frequently asked questions
- Are my figures sent anywhere?
- No. The projection runs in the page and disappears when you close it. Nothing is uploaded, stored or logged.
- When are contributions counted?
- At the end of each contribution period, which is what a standing order on the last day of the month does. Interest for a period is credited before that period's deposit is added.
- Does it account for tax and inflation?
- No. It is plain arithmetic on the rate you type. Real returns are reduced by tax, fees and inflation, so treat the result as an upper bound rather than a promise.