Compare the whole quote—not just the monthly payment
Use the same purchase price, trade-in, and fees for every lender quote, then compare APR, amount financed, monthly payment, interest, and total of payments. A longer term can make the payment look smaller while increasing the total borrowing cost.
Before you sign, match these figures
- APR: the annual cost of credit shown in the lender’s Truth in Lending disclosure.
- Amount financed: the balance being borrowed after cash, trade-in, incentives, taxes, and fees.
- Finance charge and total of payments: use the lender’s disclosed figures as final; this calculator estimates interest from the APR and entered cash flows.
- Optional add-ons: enter any financed products in the appropriate fee field instead of hiding them inside the monthly payment.
How it works
The result is built in four auditable steps. Every number in the charts and CSV comes from the same amortization schedule shown in the calculator.
- 1. Estimate the taxable amount
taxable base = max(0, vehicle price + taxable fees − trade-in value − incentives)Estimated sales tax equals the taxable base multiplied by the entered tax rate. States differ on whether trade-ins, rebates, and individual fees reduce the tax base, so replace this estimate with the buyer’s-order figure when available.
- 2. Calculate the amount financed
P = price + taxable fees + non-taxable fees + tax − cash down − (trade-in value − amount owed) − incentivesIf the trade-in loan payoff is greater than the trade-in value, the negative equity increases the amount financed.
- 3. Calculate the scheduled monthly payment
M = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1], where r = APR ÷ 100 ÷ 12At 0%, the calculator divides the financed amount evenly by the term. The tool treats the entered APR as the annual rate used for payment math; a lender’s disclosed APR can also include certain finance charges, so the signed disclosure remains authoritative.
- 4. Build the amortization schedule
monthly interest = opening balance × r; principal = payment − interestAny extra monthly payment is added after interest and applied to principal. Each row is rounded to cents, and the final payment is adjusted to bring the remaining balance to exactly zero.