Toolstia / Simple interest calculator
Simple interest calculator
With simple interest, you earn or pay interest only on the original amount. Enter the principal, the yearly rate and the time to see the interest and the total, with a year-by-year table.
Enter the amount, the yearly rate and the time.
Simple interest is worked out on the original amount only: principal x rate x time. Most savings and loans use compound interest, so use the compound interest calculator for them.
How it works
- Enter the principal and the yearly interest rate.
- Enter the time and choose years or months.
- Read the interest, the total and the table.
The formula
Interest equals principal times rate times time. With the rate as a percentage and time in years, 1,000 at 5% for 3 years earns 150, for a total of 1,150.
Months
If your time is in months, the tool divides it by 12 first, so 18 months is 1.5 years.
Simple or compound
Under compound interest, interest is added to the balance and then earns interest itself, so it grows faster over time. Some short loans and bonds use simple interest. Most bank savings use compound.
Where it appears
Short-term personal loans, some car loans, treasury bills and school problems use simple interest. Check your own agreement to see which applies.
Questions
How do I find the rate or the time?
Rearrange the formula. This tool solves for the interest and the total.
Does it work for borrowing?
Yes. Interest owed works the same way.
Is anything uploaded?
No. Your numbers stays in your browser and is never sent anywhere.