What the payment model includes
The starting loan balance is the vehicle amount plus financed fees. The required monthly payment uses fixed-rate amortization over the entered whole-year term. When extra principal is entered, the calculator applies the required payment plus the extra amount each month and stops when the remaining balance is paid.
The final payment is limited to the amount actually owed. Total repayment therefore does not multiply the extra amount through months after payoff.
Amortization formula
For balance P, monthly rate r, and n monthly payments, the required payment is P × r ÷ (1 − (1 + r)^−n). At a zero rate it is P ÷ n. The accelerated schedule adds monthly interest to the remaining balance and then applies the planned payment.
The term is always interpreted as years and converted to months. Values above the allowed auto-loan range are rejected instead of silently changing units.
Loaded example
A $32,000 vehicle amount plus $600 of financed fees at 7.2% annual interest for five years produces a required payment of about $648.60 per month. With no extra principal, payoff is 60 months and estimated total repayment is about $38,915.98.
What to verify in an offer
Confirm whether taxes, registration, optional products, negative equity, and fees are included in the amount financed. Compare the payment, finance charge, total of payments, and APR on the lender disclosure. The annual interest rate used here is not a substitute for the disclosed APR.
Payment timing, late fees, prepayment rules, daily-interest accrual, payment allocation, and a payoff quote can change actual results. Ask the lender how extra payments are applied to principal.
Consumer sources
The CFPB describes the Truth in Lending disclosure for auto loans, and the FTC discusses financing or leasing a car. Use those documents to reconcile this estimate.
Use Auto Loan Payoff for an existing balance and Auto Loan Affordability for a preliminary budget ceiling.