Simple Interest Calculator
Find simple interest from principal, rate and time, or work backward to any of them.
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Interest
- Principal
- Rate
- Time
- Total with interest
- Interest per day
- Compound Would Earn
Saved Calculations
Items you add are saved in this browser.
| Name | Principal | Rate | Years | Interest | Remove |
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How to Calculate Simple Interest
Simple interest is paid only on the original principal, never on interest already earned. It's used for many short-term loans, some auto loans, Treasury bills and bonds between coupon dates.
Interest = P × r × t Total = P × (1 + r × t)
P = I ÷ (r × t) r = I ÷ (P × t) t = I ÷ (P × r)
r is the annual rate as a decimal and t is in years. For days, divide by 365 (or 360 under the banker's rule, which some commercial loans use).
Worked Example
Simple vs. Compound
| Years | Simple (5,000 at 4%) | Compounded Yearly |
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