Simple Interest Calculator
Calculate simple interest and the final amount on a loan or deposit. Free and instant.
Simple interest formula
Simple interest = principal × rate × time. Unlike compound interest, it is always calculated on the original amount only, so growth is a straight line.
Where it is used
Short-term loans, some car loans, bonds and basic savings products use simple interest. Compare it with the compound interest calculator to see the difference over time.
Worked example
Last reviewed November 2026. Formulas are standard and shown in the sections above; results are estimates.
Tips and common mistakes
- Check whether a loan uses simple or compound interest.
- Over long periods compound interest grows much faster.
- Make sure the rate and time use the same unit (years).
Frequently asked questions
Is simple interest better than compound?
For a borrower, simple interest costs less. For a saver, compound interest earns more.
How is it different from compound interest?
Simple interest never earns interest on interest.
Can I enter months?
Yes, enter months divided by 12, for example 0.5 for six months.
Money guides for this topic
All guides →Compound Interest Explained (and Why Starting Early Wins)
How compound interest works, the rule of 72, and a simple example showing why time matters most.
Read guide →How to Save Money: 10 Practical Ways with Real Numbers
Ten proven ways to save money, each with the math showing how much you can keep every year.
Read guide →How to Make a Budget in 5 Simple Steps
A beginner-friendly guide to building a monthly budget that you can actually stick to.
Read guide →Related calculators
Compound Interest Calculator
See how savings or investments grow with monthly contributions and compound interest. Free and instant.
Open calculator →Savings Goal Calculator
Find out how much to save each month to reach your goal by a target date.
Open calculator →Savings Interest (APY) Calculator
Convert APR to APY and see how much a savings account earns with compounding.
Open calculator →Results are estimates and not financial advice.