Simple interest calculator
Interest = principal × rate × time. Cross-links to compound.
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About Simple interest calculator
Calculate simple interest as principal × rate × time, plus ending amount — offline, no compounding.
Simple interest is the straight line: Interest = P × r × t, Amount = P + Interest. The interest does not get added back into the base during the term. Short personal notes, some classroom problems, and a few consumer products still quote money this way.
Enter principal, annual rate, and years (fractions allowed for partial years). You get interest and total amount. That is the whole tool. No chart of compounding, because there is nothing compounding to chart.
If a product pays or charges interest on interest, you want the compound interest calculator instead. If you are comparing 'years to double', rule of 72 is the napkin version of compound growth, not simple interest.
How to use Simple interest calculator
- 1Enter principal, annual rate as a percent, and time in years.
- 2Read interest earned or owed and the total amount.
- 3Open compound interest when the product compounds.
What it won't do
- No compounding and no amortization schedule.
- Single rate for the whole term.
Common questions
When should I use compound interest instead of simple?
Whenever interest itself earns interest — savings accounts, most investments, and amortizing loans on the lender side. Use simple interest when the agreement literally says interest is P×r×t with no compounding.
Can I enter months instead of years?
Enter years as a decimal (six months ≈ 0.5). The formula is annual rate times time in years.
Does simple interest include fees?
No. Origination fees and penalties are outside the formula. Adjust principal yourself if you need a fee-inclusive picture.
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Why this one doesn't upload your file
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