Interest without compounding. The Simple Interest Calculator takes principal, annual interest rate, time and returns simple interest plus total amount, interest per month. Results update as you type, and the formula is shown under the result so you can repeat it in your own spreadsheet.
Investment maths is about comparing money at different points in time on a fair basis. Compound rates, discounting and annualised returns let you compare options of different sizes and durations. Use the worked example below to check the maths against your own figures.
How the Simple Interest Calculator works
Simple interest is charged only on the original principal, never on accumulated interest, so it grows in a straight line. Short-term loans, some deposits and late-payment charges use it.
Worked example
With the example values (principal of $10,000, annual interest rate of 8%, time of 3 years), the simple interest is $2,400.00; total amount $12,400.00, interest per month $66.67. Change any figure above and the result updates immediately; use Copy results to paste the summary into a note or email.
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Frequently Asked Questions
How is simple interest calculated?
interest = principal × rate × time.
Which figures do I need?
Principal, annual interest rate, time. Take them from the same period and the same set of accounts or reports so the ratio is consistent, and check the example values as a guide to the units expected.
Does the calculator account for taxes and fees?
Only where there is an input for them. For a true net return, add fees and taxes to your inputs or use the stock and crypto profit calculators, which include them.
