Compound interest calculator
See how a starting balance grows with compound interest. Compare rates, time horizons and compounding frequencies.
Result for the values shown.
Calculations run in your browser.
What to enter
| Input | Meaning and units |
|---|---|
| Starting balance | Enter starting balance using the definition in the method and example. |
| Annual interest rate (%) | Enter percentage units: 5 means 5%, not a fraction of 0.05. |
| Time period (years) | Enter time period in years; use the same basis as the other measurements. |
| Compounding | Choose how often interest is added. Keep the nominal rate on an annual basis. |
Understanding your result
The outputs describe the mathematical scenario you entered. Assumed rates, timing and included costs determine the result; an estimate is not an offer or eligibility decision.
Common mistakes
- Mixing annual and monthly periods, or leaving out a cost that the model does not include.
Check your calculation
- Compare a simple one-period or zero-change case with hand arithmetic before applying a longer scenario.
Calculation checks, sources and review limits
How much will my starting balance grow with compound interest?
Enter your starting balance, assumed annual rate, years and compounding frequency to estimate the future balance and interest earned. This model includes no additional contributions.
Common uses
- Compare growth over different time horizons.
- Compare annual and monthly compounding at the same nominal rate.
How it works
Each compounding period adds interest to the balance. The next period earns interest on that larger amount. This model uses a constant nominal annual rate and no additional deposits. It excludes fees, taxes and inflation. Fractional years use an exponential projection.
Worked example
1,000 at 5% a year, compounded annually for 10 years, grows to 1,628.89. Interest earned is 628.89.