Formula
I = P × r × t
P is the principal, r the interest rate per period and t the number of periods. The total amount is P + I.
Example
$10,000 at 5% per year for 3 years earns $1,500 in simple interest, for a total of $11,500.
Simple vs. compound interest
With simple interest the interest never earns interest. Most savings accounts and loans use compound interest, which grows faster over time. Simple interest appears in some short-term loans, bonds and car loans calculated on the original amount.
Frequently asked questions
Can I use a monthly rate?
Yes. Choose "per month" as the rate period; the calculator converts everything to the same unit.
Results are estimates for information only and are not financial, legal or medical advice. Rates, taxes and fees vary — confirm with a professional or your lender.