Simple Interest Calculator
Compute simple interest with year, month, or day time input.
Premium
Full Interest Suite
Compare simple vs compound interest, model different compounding frequencies, and generate amortization tables.
Frequently Asked Questions
What is simple interest?
Simple interest is calculated only on the original principal. The formula is I = P × r × t, where P is principal, r is the annual interest rate, and t is the time in years.
How is simple interest different from compound interest?
Compound interest is calculated on both the principal and previously accumulated interest, so it grows faster over time. Simple interest stays proportional to the original principal throughout.
When is simple interest used?
Simple interest is commonly used for short-term loans, car loans, and some savings accounts. It is also used in treasury bills and certain bonds.