Simple Interest Calculator

Calculate simple interest I = P × r × t and the total amount repaid or earned on a loan or deposit.

$
%
years
Fractions allowed: 6 months = 0.5.
Interest
$880.00
Total (principal + interest)
$4,880.00
Interest per year
$220.00
Interest per month
$18.33

Estimate generated with SortedSums: https://sortedsums.com/simple-interest-calculator/. For informational purposes only; verify before relying on it.

Estimate only. This tool is for informational and educational purposes. Results depend on your inputs and simplifying assumptions, and are not a substitute for professional engineering, design or financial advice. Always verify with a qualified professional and applicable codes before purchasing, building or making decisions.

How it’s calculated

Simple interest is charged only on the original principal, never on interest already earned, so it grows in a straight line.

I = P × r × t Total = P + I

Example (OpenStax Contemporary Mathematics): $4,000 at 5.5% for 4 years earns I = 4,000 × 0.055 × 4 = $880, for a total of $4,880.

Frequently asked questions

Simple vs compound interest?

Simple interest is on the principal only; compound interest also earns on past interest, so it grows faster over time.

Where is simple interest used?

Short-term loans, some auto loans (daily simple interest), and the coupon payments on many bonds.

How do I enter months?

Divide months by 12. 18 months = 1.5 years.

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Sources

Formulas are taken from the free public references above. Results are provided “as is” for informational and educational purposes only. See our disclaimer.

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