Simple Interest Calculator
Calculate simple interest, principal, time, or interest rate.
Simple interest is computed on the original principal without compounding.
Result
How to use this calculator
Simple interest is computed on the original principal without compounding. Enter amounts in the units shown, select the applicable options, and click Calculate. Use Reset to restore the starting values.
Calculation formula
A = P × (1 + r × t).
Assumptions and accuracy
Review timing, rates, fees and result notes when comparing scenarios. Future returns and rates are assumptions rather than guaranteed outcomes. Monetary display follows the currency’s precision; intermediate calculations retain additional digits.
Choose what to calculate
Simple interest calculator for principal rate and time
Calculate noncompounding interest, or solve for principal, rate or term. Confirm the entered time unit before comparing an annual quote.
Open this calculationUnderstanding this calculation
Calculate simple interest without interest-on-interest. Match the rate's time unit with the duration before solving for balance, principal, time or rate.
Worked examples
Simple interest on 10,000 for four years
Illustrative inputs are specified in the steps below; the example link loads the complete settings. Unmentioned settings use the linked defaults.
- Interest = 10,000 × 5% × 4 = 2,000. Add the original 10,000 to obtain 12,000; interest itself does not earn interest.
Balance: 12,000 USD.
Try these inputsCommon questions
How is simple interest different from compound interest?
Simple interest is based on the original principal. Compound interest also earns on previously accumulated interest.
Can I enter a monthly rate with a term in years?
Choose the correct rate and term units so the tool can normalize them. A monthly percentage should not be entered as an annual percentage.
Scope and assumptions
This model does not describe compound-interest accounts or every loan's daily accrual convention.
Sources
- Calculation methodology, rule versions and testing limitations
- Reference calculator for feature comparison (not a model-parity certification)
Calculation notes checked . Examples are mathematical checks under the stated assumptions.
Calculation methods and formulas
Balance
Simple interest is computed on the original principal without compounding.
A = P × (1 + r × t).
Principal
Simple interest is computed on the original principal without compounding.
A = P × (1 + r × t).
Term
Simple interest is computed on the original principal without compounding.
A = P × (1 + r × t).
Rate
Simple interest is computed on the original principal without compounding.
A = P × (1 + r × t).
See our calculation methodology and review status for data versions, rounding and validation limitations.