Interest Calculator
Enter an amount, a rate and a time. We show the simple interest and, for comparison, what monthly and yearly compounding would give.
This calculator gives estimates for information only. It is not financial, tax or legal advice. Real results depend on lender terms, fees and local rules.
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The formula
Simple: P x R x T. Compound: P x (1 + R/n)^(nT) - P.
Two ways to earn interest
With simple interest the amount you earn each year is fixed. With compound interest the interest is added to your balance, so next year you earn interest on a bigger number.
Side by side
On 10,000 at 6 percent for 10 years: simple interest gives 6,000. Compounding monthly gives about 8,194, and yearly compounding about 7,908. The longer the time, the bigger the gap.
Which one applies to me?
Check the terms of your account or loan. Savings and investments usually compound. Some fixed-term loans use simple interest.
Examples to check
Type these into the calculator above to see how it behaves. Every result below was produced by the same calculator code that runs on this page.
| What you enter | What you get |
|---|---|
| Principal ($): 1000; Annual interest rate (%): 5; Years: 3 | Simple interest: $150.00 |
| Principal ($): 10000; Annual interest rate (%): 6; Years: 10 | Simple interest: $6,000.00 |
| Principal ($): 2500; Annual interest rate (%): 4.5; Months: 18 | Simple interest: $168.75 |
Interest Calculator: frequently asked questions
What is the difference between simple and compound interest?
Simple interest is calculated on the original amount only. Compound interest is calculated on the amount plus the interest already earned, so it grows faster over time.
Is this financial advice?
No. It gives an estimate from the numbers you enter. Real offers depend on fees, tax and the lender or provider, so check the terms before you commit.
Is what I enter in this calculator saved or sent anywhere?
No. The calculation runs in your browser, so what you enter is not sent to our servers. We only count, anonymously, whether a tool ran successfully.
Is this calculator free to use?
Yes. It is free, needs no sign-up and has no usage limit.
Last reviewed: October 3, 2026