Simple interest calculator
Calculate interest earned or owed when interest is based only on the starting principal, without compounding.
Result for the values shown.
Calculations run in your browser.
What to enter
| Input | Meaning and units |
|---|---|
| Principal | Enter principal using the definition in the method and example. |
| Annual rate (%) | Enter percentage units: 5 means 5%, not a fraction of 0.05. |
| Time (years) | Enter time in years; use the same basis as the other measurements. |
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 interest is earned without compounding?
Enter principal, assumed annual rate and time in years. The calculation applies interest to the original principal throughout the period.
Common uses
- Estimate interest under a simple-interest model.
- Compare simple interest with compound interest using the same inputs.
How it works
Multiply principal by the annual rate as a decimal and the time in years. Add interest to principal to get the total. Fractional years are supported; if converting days to years, choose the day-count convention appropriate to your agreement.
Worked example
1,000 at 5% simple annual interest for 3 years earns 150, for a total of 1,150.