Compound interest calculator
Project how a starting balance and monthly deposits grow with compound interest.
| Year | Contributed | Balance |
|---|---|---|
| 1 | $8,000 | $8,392 |
| 2 | $11,000 | $11,994 |
| 3 | $14,000 | $15,817 |
| 4 | $17,000 | $19,877 |
| 5 | $20,000 | $24,187 |
| 6 | $23,000 | $28,762 |
| 7 | $26,000 | $33,620 |
| 8 | $29,000 | $38,778 |
| 9 | $32,000 | $44,253 |
| 10 | $35,000 | $50,067 |
| 11 | $38,000 | $56,239 |
| 12 | $41,000 | $62,791 |
| 13 | $44,000 | $69,748 |
| 14 | $47,000 | $77,134 |
| 15 | $50,000 | $84,975 |
| 16 | $53,000 | $93,300 |
| 17 | $56,000 | $102,139 |
| 18 | $59,000 | $111,522 |
| 19 | $62,000 | $121,484 |
| 20 | $65,000 | $132,061 |
How it works
Each month the balance earns interest at the annual rate divided by 12, then your contribution is added. The new balance earns interest the next month, which is what compounding means.
Real returns vary and are not guaranteed. Investment returns can be negative, and this tool ignores taxes, fees, and inflation.
Example
With the sample inputs shown above (Starting balance ($) = 5000; Monthly contribution ($) = 250; Annual rate (%) = 6; Years = 20), the calculator returns: Ending balance: $132,061 (After 20 years); You contributed: $65,000; Interest earned: $67,061.
Things to know
Time matters more than the starting amount. Try changing the years from 20 to 30 and compare the ending balance. The tool assumes a constant return, while real investments rise and fall, so use a conservative rate for planning.