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Interest Calculator
Calculate simple interest earned or owed on any principal amount over a given rate and time period.
Your numbers
$
%
yrs
Total interest
$0
Simple interest over the period
Principal$0
Interest earned$0
Final balance$0
How the interest calculator works
Simple interest is calculated only on the original principal, not on interest already earned. It is common for short-term loans and basic savings estimates.
Interest = Principal × Rate × Time (rate as a decimal, time in years)
Frequently asked questions
How is this different from compound interest?+
Simple interest is charged only on the principal. Compound interest is charged on the principal plus accumulated interest, so it grows faster over time.
Can I use it for months?+
Enter the time in years — for example, 0.5 for six months.