How the auto loan calculator works
Enter the vehicle price, down payment, trade-in value, interest rate, loan term in months and your sales-tax rate. Sales tax is added to the amount financed; the down payment and trade-in are subtracted. The monthly payment is the standard fixed-payment loan formula on what is left.
The formula
Amount financed = price − down payment − trade-in + price × sales-tax rate; monthly payment M = P × r(1+r)^n / ((1+r)^n − 1) with r the monthly rate and n the term in months.
Sales tax here is applied to the full vehicle price. Many states tax only the price after the trade-in, which would make your real amount financed a little lower. Dealer fees, title and registration are not included.
Frequently asked questions
Does the trade-in reduce my loan?
Yes. The trade-in value is subtracted from the amount you finance, the same as a down payment.
Is sales tax included in the payment?
Yes — sales tax on the vehicle price is added to the amount financed, so it is spread across your payments.
Is a longer loan term better?
A longer term lowers the monthly payment but raises the total interest. Compare 48, 60 and 72 months in the calculator to see the trade-off.
What is not included?
Dealer documentation fees, title, registration and any add-ons. Add them to the price if you are financing them.
Results are estimates for planning, not financial advice. Last reviewed 2026-09-28.