How to use it
- Choose what to solve for: the ending balance by default, or the deposit, return, years or starting amount (then enter a target).
- Enter amounts, rate, years and compounding; More options adds yearly deposit increases and inflation.
- Read the result, the breakdown chart and the yearly schedule, and export CSV for further analysis.
Growth of 10,000 with compound interest
Compounded annually with no further deposits. Both rate and time magnify compounding: at 7%, 20 years gives 3.9× and 30 years 7.6×.
| Annual rate | 5 years | 10 years | 20 years | 30 years |
|---|---|---|---|---|
| 3% | 11,593 | 13,439 | 18,061 | 24,273 |
| 5% | 12,763 | 16,289 | 26,533 | 43,219 |
| 7% | 14,026 | 19,672 | 38,697 | 76,123 |
| 10% | 16,105 | 25,937 | 67,275 | 174,494 |
Effect of compounding frequency
At the same 5% nominal rate, more frequent compounding gives a higher effective rate, though monthly to daily adds little. Compare products by effective annual yield (APY), not the nominal rate (APR).
| Compounding | Effective annual rate |
|---|---|
| Annually | 5.000% |
| Quarterly | 5.095% |
| Monthly | 5.116% |
| Daily | 5.127% |
| Continuously | 5.127% |
Frequently asked questions
Compound vs simple interest?
Simple interest pays on the principal only; compound interest also pays on interest already earned, and the gap grows with time. 10,000 at 5% for 30 years: 25,000 simple vs 43,219 compound.
Start vs end-of-period deposits?
Deposits at the start earn one extra period of interest. 1,000 a month at 6% for 10 years is about 163,879 at the end of each month vs 164,699 at the start.
How accurate are the results?
Formulas are exact and compounding is simulated period by period, shown to the cent. Real returns fluctuate and banks differ on day counts, tax and fees, so use the results for planning and comparison.