Simple Interest CalculatorFree online financial calculator — instant results, no sign-up
Interest earned without compounding.
Estimates only, based on the inputs and assumptions shown. This is not financial, investment, tax, or legal advice. Prices, rates and local rules may change; crypto scenarios do not predict returns. Confirm important decisions with a qualified professional.
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About the Simple Interest Calculator
This calculator determines the total simple interest and the final balance for an investment or loan where interest does not compound. It is commonly used by individuals evaluating short-term loans, basic promissory notes, and simple fixed-rate debt agreements.
- Principal
- The starting amount borrowed or invested, entered in dollars ($).
- Rate
- The annual interest rate entered as a percentage (%).
- Years
- The total duration of the loan or investment term in years.
Formula and method
I = P × (r / 100) × t A = P + I
- ITotal simple interest accrued
- PPrincipal amount
- rAnnual interest rate (percentage)
- tTime in years
- AEnd balance (principal plus accumulated interest)
The interest is calculated by multiplying the principal by the decimal interest rate and the number of years. The resulting interest is then added to the original principal to produce the final end balance.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Principal10000 $
- Rate5 %
- Years3 years
Results
- Interest$1,500.00
- End balance$11,500.00
How to use the Simple Interest Calculator
- 1Enter the initial principal amount.
- 2Input the nominal annual interest rate as a percentage.
- 3Specify the duration of the term in years.
- 4Read the total interest payable or earned and the combined end balance.
Reading your result
The Interest figure reflects the linear dollar earnings or borrowing cost accumulated strictly on the initial principal. The End balance represents the full amount due at maturity or the final value of the account after the given term.
Limitations
This calculation assumes interest is never added back to the principal to earn additional interest (no compounding). It does not factor in taxes, ongoing fees, amortization payment schedules, or inflation.
Common questions
How does simple interest differ from compound interest?+
Simple interest is calculated only on the initial principal balance for the entire duration. Compound interest calculates interest on both the initial principal and any accumulated interest from previous periods.
How do I calculate simple interest for periods less than a full year?+
Convert the term into a fraction of a year for the Years input. For example, 6 months is entered as 0.5 years, and 90 days can be entered as 90 divided by 365 (approximately 0.2466 years).
Which financial products typically use simple interest?+
Auto loans, personal installment loans, short-term promissory notes, and certain government bonds frequently use simple interest calculations rather than daily or monthly compounding.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.