Interest Calculator
The Interest Calculator finds the simple interest earned or owed on a principal amount over a given time period at a fixed annual rate.
Simple Interest Earned
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Principal--
Total (Principal + Interest)--
The simple interest formula
Simple interest grows linearly rather than compounding, and is calculated as:
I = P × r × t
Where I is interest, P is the principal, r is the annual interest rate (as a decimal), and t is time in years.
Example: $10,000 at 5% simple interest for 3 years earns $10,000 × 0.05 × 3 = $1,500 in interest, for a total of $11,500.
Simple vs. compound interest
Simple interest is calculated only on the original principal, while compound interest is calculated on the principal plus any interest already earned, so it grows faster over time. Most savings accounts, credit cards, and long-term investments use compound interest — see our Compound Interest Calculator to compare.