Simple Interest Calculator
Enter a principal, an annual rate and a length of time to see the simple interest and the total amount. You can also solve for the principal, the rate or the time when you know the interest. Time can be in years, months or days, on a 365 or 360 day year, and a table sets simple interest beside interest compounded yearly. Everything runs in your browser.
| Year | Simple interest | Compounded yearly |
|---|---|---|
| 1 | 5,225.00 | 5,225.00 |
| 2 | 5,450.00 | 5,460.12 |
| 3 | 5,675.00 | 5,705.83 |
Simple interest is paid only on the original amount: I = P x r x t, with the rate as a yearly figure and the time in years. Because the interest is never added to the principal, the balance grows in a straight line, while compound interest grows faster each year. Time in months is divided by 12, and time in days is divided by 365, or by 360 if your lender uses a 360 day year. Any one of the principal, rate or time can be found from the other two and the interest. Everything is worked out in your browser and nothing is uploaded.
Related Tools
[5 suggestions]Compound Interest Calculator
See how a starting amount and monthly deposits grow with compound interest, year by year, with the effective annual rate.
Math & MoneyAPR to APY Calculator
Convert a nominal annual rate (APR) to the effective yearly rate (APY) and back for any compounding, and see the balance after a number of years.
Math & MoneyLoan Payment Calculator
Work out the monthly payment on a fixed-rate loan, the total interest and a full amortization schedule, with optional extra payments.
Math & MoneyCAGR Calculator
Find the compound annual growth rate between two values, the value after growing at a rate, or the time to reach a target, with the doubling time and rule of 72.
Math & MoneyPercentage Calculator
Find a percentage of a number, what percent one number is of another, a percentage increase or decrease, or a number raised or lowered by a percentage.
Math & MoneyAbout the Simple Interest Calculator
Simple interest is paid only on the original amount, the principal: I = P x r x t, with the rate written as a yearly percentage and the time in years. The total amount is the principal plus the interest. For 5,000 at 4.5 percent for 3 years, the interest is 5,000 x 0.045 x 3 = 675.00, and the total is 5,675.00. Because the interest is never added to the principal, the balance grows in a straight line, while compound interest grows faster each year: the same 5,000 compounded yearly reaches 5,705.83 after 3 years, and after 10 years 7,764.85 against 7,250.00 for simple interest. Any one of the four values can be found from the others. The principal is I / (r x t), the rate is I / (P x t) and the time is I / (P x r). Time in months is divided by 12, and time in days is divided by 365, or by 360 if your lender uses a 360 day year, as some commercial loans do, so 90 days at 6 percent on 10,000 is 147.95 on a 365 day year and 150.00 on a 360 day year. Simple interest is common on short loans, some car loans, bonds that pay a fixed coupon and in school math. Nothing is uploaded.
What is the simple interest formula?▾
I = P x r x t, where P is the principal, r is the annual rate as a decimal and t is the time in years. For 1,000 at 5 percent for 3 years, I = 1,000 x 0.05 x 3 = 150, and the total amount is 1,150.
What is the difference between simple and compound interest?▾
Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus the interest already added, so it grows faster. For 5,000 at 4.5 percent over 10 years, simple interest gives 7,250 and yearly compounding gives 7,764.85.
How do I calculate simple interest for months or days?▾
Convert the time to years first: divide months by 12 and days by 365, or 360 if your lender uses a 360 day year. For 90 days at 6 percent on 10,000, the time is 90 / 365 of a year, so the interest is 147.95.
How do I find the rate or the time?▾
Rearrange the formula. The rate is I / (P x t) and the time is I / (P x r). Choose the Rate or Time tab, enter the other values and the interest, and the tool gives the answer.
Is my data uploaded?▾
No. The calculation runs in your browser and the amounts you enter are not sent anywhere.