Simple interest calculator
Interest earned or owed on a principal that does not compound.
Enter your values and press Calculate. Your inputs stay in the address, so you can switch language or share the link.
Formula
I = P × r × t A = P + I
How it works
Simple interest is charged only on the original amount: I = P × r × t. It grows in a straight line, unlike compound interest.
Worked example
The same calculation with the default values:
- Principal 5,000
- Annual interest rate 4.5 %
- Years 3
- I = 5,000 × 4.5 ÷ 100 × 3 = 675
- A = 5,000 + 675 = 5,675
Result: Interest: 675.00 USD · Total amount: 5,675.00 USD
Simple interest is calculated only on the original principal, never on accumulated interest - most real savings accounts and many loans actually use compound interest, so this figure will understate growth (or cost) compared to a compounding product over the same period.
Common mistakes
- Using this calculator for a savings account or loan that actually compounds (most do) - the real result will grow faster than this simple-interest figure shows.
- Entering the rate as a decimal (0.05) instead of a percentage (5) - this field expects a percentage.
- Forgetting that the time period must be in years to match the annual rate; a term quoted in months needs converting first (divide by 12).
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