Calculate monthly payments, total interest, and amortization
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Enter a loan amount, interest rate, and term to get the fixed monthly payment, total interest paid, and total cost of the loan. It works for any amortized loan — auto, personal, student, or small business — and runs entirely in your browser with no signup or data collection.
Adjust one input at a time to see exactly how the payment and lifetime interest respond.
A $25,000 auto loan at 7% for 60 months costs $495 per month and about $4,700 in total interest. Stretch it to 72 months and the payment drops to $426 — but total interest climbs to roughly $5,680. The longer term costs almost $1,000 more for the same car; whether that trade is worth $69 a month of breathing room is exactly the decision this tool makes visible.
With the standard amortization formula: payment = P × r / (1 − (1+r)^−n), where P is the principal, r the monthly rate (annual rate ÷ 12), and n the number of months. Every fixed-rate installment loan uses this math.
Interest accrues on the outstanding balance each month. A longer term keeps the balance high for more months, so more total interest accrues — even though each individual payment is smaller.
The interest rate drives the payment math; APR folds in mandatory fees (origination, etc.) to give a truer cost of borrowing. When comparing offers, compare APRs — a low rate with a big origination fee can lose to a higher rate with none.
Substantially, if the loan has no prepayment penalty. Extra principal reduces the balance that interest accrues on, shortening the loan. Even one extra payment per year on a 60-month loan typically shaves several months off the end.