Simple Interest Calculator
Calculate simple interest using principal, rate, and time. Find total interest earned and final amount for basic interest calculations. Figures never leave your device — every calculation runs locally in your browser.
How to Use the Simple Interest Calculator
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Frequently Asked Questions
What is the simple interest formula?
SI = P × R × T / 100, where P = principal, R = annual interest rate (%), T = time in years. Total amount = P + SI.
How is this different from compound interest?
Simple interest is calculated only on the principal. Compound interest is calculated on principal plus accumulated interest. Simple interest produces lower returns over time.
What time units are supported?
Years only — the time field is a plain year count. Convert months or days to fractional years yourself before entering.
When is simple interest used?
Short-term loans, car loans, some personal loans, and educational examples. Most mortgages and long-term investments use compound interest.
When using Simple Interest Calculator, is my data stored?
No. All calculations run locally in your browser. No financial data is transmitted.
Can you work the default example?
$10,000 at 5% for 3 years gives Simple Interest $1,500.00, Total $11,500.00, and Annual interest $500.00 (principal × rate ÷ 100 × years). Try the $50k/8%/5yr preset: $20,000 interest on a $70,000 total.
Last updated October 2026