How to use this calculator
Solve interest, ending balance, principal, rate or term using simple interest. Choose compatible rate and time periods; the conversion uses twelve months or 365 days per year without compounding.
- Enter solve for, interest period, starting balance and review the remaining options.
- Select Calculate or change a value to update the result. Read the result label and units before copying.
- Use Reset to restore the worked starting values.
Formula and method
The entered model uses a fixed 365-day year and equal months. It does not implement lender-specific actual/360 or actual/actual conventions.
Worked example
1,000 at 5% for 3 years earns 150 interest.
Questions about simple interest calculator
How is simple interest different from compound interest?
Simple interest applies the rate only to the original principal. At 5% for three years, 1,000 earns 150. Compound interest also applies to accumulated interest, so the comparison depends on compounding frequency.
What assumptions should I check?
The entered model uses a fixed 365-day year and equal months. It does not implement lender-specific actual/360 or actual/actual conventions.
Are my inputs saved?
Calculations run in your browser. We store only tool IDs for favorites and recent tools. Sharing inputs in links is disabled for this category.
Financial tools model the assumptions shown above and do not predict actual returns or replace lender disclosures or professional advice. Amounts are currency-neutral: use the same currency for every amount. No exchange rate is applied.