Simple Interest Calculator
Interest on a loan or deposit from principal times rate times time.
Calculate simple interest
Estimated result
Simple interest
- Principal plus interest
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- Average monthly equivalent
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No compounding, fees, taxes, payments, or changing principal are modeled.
Your entries and results stay in this browser. This tool does not send, save, or add them to the page address.
How to use this calculator
Enter the original principal, annual simple-interest rate, and time in years. The result shows interest and principal plus interest.
Formula and limitations
The formula is I = P × r × t. It assumes the principal never changes and interest never compounds. Fees, payment timing, taxes, day-count rules, and lender rounding are excluded.
The average monthly figure is total interest spread evenly across the months in the period. It is not a payment, an accrual schedule, or a cash flow you would actually see; nothing is paid or added during the term in this model.
This is an educational estimate, not a quote, an offer, or financial advice. Confirm actual terms with the relevant institution.
Frequently asked questions
What formula is used?
Simple interest equals principal multiplied by the annual rate as a decimal and time in years.
Does this calculator compound interest?
No. Interest is calculated only on the original principal.
Is the monthly figure a payment schedule?
No. It is only total interest divided evenly across the entered months.