Simple Interest Calculator
Calculate simple interest and the total amount for any principal, rate and time period.
Runs in your browser — nothing is uploadedEnter values
Time in
Result
- Total amount
- $12,400.00
- Principal
- $10,000.00
- Time in years
- 3
How it's calculated
Interest = P × R × T ÷ 100
= $10,000.00 × 8 × 3 ÷ 100 = $2,400.00
About Simple Interest Calculator
Simple interest is calculated only on the original amount (the principal), not on interest already earned. It is used for many short-term loans, some savings products, car loans in some countries and in school and exam maths.
Enter the principal, the yearly rate and the time in years, months or days to see the interest and the total amount. The formula is shown so you can check the working.
When to use it
- Short-term personal loans and borrowing between family or friends.
- Fixed deposits or bonds that pay simple interest.
- Maths homework and exam preparation.
- Quickly estimating interest before comparing with compound interest.
Tips for better results
- Convert months to years by dividing by 12 (or let the calculator do it).
- For periods over a year, compound interest gives a higher return than simple interest at the same rate.
- Check whether a loan uses simple or compound interest — it changes the real cost.
How to use the Simple Interest Calculator
- Enter the principal and yearly rate.
- Enter the time in years, months or days.
- See the interest and total.
Frequently asked questions
What is the simple interest formula?
Interest = Principal × Rate × Time ÷ 100, with the rate per year and time in years.
Simple vs compound interest?
Simple interest is only earned on the original principal. Compound interest also earns interest on previously earned interest.
How is interest calculated for days?
The yearly rate is divided by the number of days in a year (commonly 365) and multiplied by the number of days. Some banks use 360 days, which gives slightly more interest.
When is simple interest used?
It is common for short-term loans, some auto loans, certain bonds and informal lending. Most savings accounts and credit cards use compound interest instead.