Simple Interest Calculator
Last updated: June 13, 2026Interest and total from principal, rate and time.
The Simple Interest Calculator works out the interest and final amount on a principal using the classic I = P x R x T formula. Enter your principal, the annual rate and the term in years, and it instantly returns the total interest plus the final balance you repay or receive. Because simple interest is charged only on the original principal, the result is exact and easy to verify. It runs entirely in your browser, free and with no sign-up.
Disclaimer: This calculator is for informational and educational purposes only and is not financial advice. Actual figures depend on your provider, interest rates, fees, taxes and personal circumstances. Consult a qualified financial professional before making financial decisions.
How to use Simple Interest Calculator
The Simple Interest Calculator turns the principal, annual rate and time into the interest owed and the final amount in one step. It is built for fixed-deposit interest, short-term personal loans, car notes and bond coupons where interest never compounds. Type three numbers and read the answer below instantly, with nothing uploaded and no account required.
Read the full guide: Simple Interest Calculator: P x R x T (Free Online)
- 1Enter the principal, the lump sum you are lending, borrowing or investing.
- 2Add the annual interest rate as a percentage, such as 7.5.
- 3Set the term in years (use a decimal like 0.5 for six months) to see the total interest and final amount.
Interest stays flat
Because it only ever charges the original principal, the interest is the same every year and never snowballs like compound interest.
Total cost upfront
It splits the result into interest earned and the final amount, so you see exactly what you repay or collect at maturity.
Handles part-years
Enter the term as a decimal to price loans or deposits that run for months rather than whole years.
Fixed deposit interest payout
Check what a bank fixed deposit or term deposit that quotes simple interest will pay before it matures. Enter the deposit amount, the advertised annual rate and the number of years locked in to see the flat interest you earn and the maturity value, making it easy to compare two banks at a glance.
Short-term personal loan cost
Many personal and payday-style loans quote a flat simple interest charge rather than compounding. Plug in the borrowed amount, the stated rate and the loan term to see the total interest added and the full repayment, so you know the true cost before you sign and can sanity-check a lender's figure.
Car loan flat interest check
Some auto dealers advertise a flat rate where interest is figured on the full original price for the whole term. Use the principal, that flat annual rate and the number of years to estimate the simple interest portion and the total payable, which helps you spot when a flat rate is pricier than it first sounds.
Bond coupon interest per year
For a bond or note that pays a fixed coupon, simple interest gives the yearly payment instantly. Enter the face value as the principal, the coupon rate and one year to see a single year's interest, or a longer term to total the coupons received over the holding period before redemption.
Simple Interest Calculator — frequently asked questions
What is the simple interest formula?
Simple interest is 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. The final amount is A = P + I, which equals P x (1 + R x T).
How is simple interest different from compound interest?
Simple interest is always calculated on the original principal alone, so each year adds the same amount. Compound interest adds earned interest back to the balance, so later interest is charged on a growing total and the two diverge over time.
What units should the rate and time use?
The rate is an annual percentage and the time is in years, and they must match. Enter 7 for 7 percent and 2 for two years. For nine months, enter 0.75 years so the rate and term line up.
Is this calculation accurate?
Yes. Simple interest is an exact arithmetic formula with no rounding or estimation. The tool multiplies principal by rate by time and adds it to the principal, giving the same figure you would get by hand.
Is my data private?
Completely. Every calculation happens locally in your browser. Your principal, rate and term are never sent to a server, stored or shared, and no sign-up is needed.
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