Simple Interest Calculator
Compute non-compounding interest with mathematical precision. Simple interest applies to short-term loans, promissory notes, auto financing, and flat-rate bonds where interest does not compound upon itself.
Initial amount borrowed or deposited
Stated flat annual percentage rate (R)
Duration of the note or loan term (T)
Principal balance plus accumulated simple interest (P + I)
How to Use This Calculator
- Enter the original principal amount deposited or borrowed.
- Input the annual interest rate agreed upon in the contract.
- Set the duration in years using the slider.
- View the total interest generated and the combined final repayment value.
Formula & Calculation Methodology
Unlike compound interest, simple interest is computed exclusively against the original principal balance and never recalculates upon prior interest payments.
Worked Example
$15,000 principal at 6.0% annual simple interest for 4 years
Frequently Asked Questions
How does simple interest differ from compound interest?↓
Simple interest is calculated only on the starting principal. In contrast, compound interest adds accumulated interest back into the principal balance, generating interest upon interest over successive cycles.
What types of consumer products use simple interest?↓
Most retail auto loans, peer-to-peer promissory notes, short-term commercial paper, and federal student loans accrue using a daily simple interest methodology rather than compounding.
Can simple interest be computed for months or days?↓
Yes. Divide months by 12 (e.g. 6 months = 0.5 years) or days by 365 (e.g. 90 days = 90/365 ≈ 0.2466 years) to convert any duration into fractional years (T).
Is simple interest advantageous for borrowers or lenders?↓
Simple interest is generally advantageous for borrowers: extra principal payments immediately reduce the daily interest accrual without compounding penalty.
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Source Citation & Disclaimer
Informational tool only; not licensed tax, legal, or financial advice.