Simple Interest Calculator

How to use Simple Interest Calculator

Simple interest equals principal × annual rate × years. Interest does not itself earn interest in this model.

1. Enter principal, annual simple interest rate (%), years.
2. Check that the input follows the stated limits and uses consistent units.
3. Run the calculator, review the result, then copy or download it.

Good to know

• Nonnegative principal, rate 0–1,000%, and duration 0–100 years. Fractional years are used directly; no day-count convention is inferred.
• Decimal inputs have at most 120 characters and magnitude from 1e-100 to 1e15, or zero. Floating-point results are rounded to 12 significant digits; extreme derived results may underflow or be rejected. Exact integer results are identified separately.
• Educational estimate with user-entered assumptions, not a quote or financial/tax advice. Rates are hypothetical, fixed, and not fetched. Fees, taxes, inflation, payment-day conventions, and currency rules are excluded unless explicitly entered.