Monthly Payment
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Total Payment
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Total Interest
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Simple interest and loan interest calculations
Use the tools below to calculate simple interest (I = P × R × T) or estimate total loan interest on an amortizing loan. For simple vs compound interest in one place, see our simple interest calculator. For monthly payments, try the loan calculator, car loan calculator, or personal loan calculator.
Estimate how much interest you will pay on a loan with fixed monthly payments (amortizing loan). Enter principal, rate, and term to see total interest.
Monthly Payment
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Total Payment
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Total Interest
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Calculate simple interest using the formula I = P × R × T, where P is principal, R is the annual rate (as a decimal), and T is time in years. Used for some short-term loans, savings, or bonds.
Simple Interest (I)
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Total Amount (P + I)
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These interest calculators provide estimates for informational purposes only. Return to the LoanWise home page.
Simple interest is calculated on the original principal only: I = P × R × T. The interest does not compound. It’s common for some short-term loans, certificates of deposit, or bonds. Loan interest (amortizing) applies to most mortgages, auto loans, and personal loans—interest is charged on the remaining balance each month, so early payments are mostly interest and later payments are mostly principal. Total interest on an amortizing loan is higher than simple interest over the same period for the same rate.
Use the simple interest calculator when you know principal, annual rate, and time in years and want the interest or total. Use the loan interest calculator when you have a loan with fixed monthly payments and want to see total interest, monthly payment, and total payback.