Auto Loan Calculator

An auto loan is a fixed-payment amortizing loan: every month you pay the same amount, with the early payments mostly covering interest and the later ones mostly paying down principal. This calculator builds the loan from the deal itself — vehicle price, sales tax, down payment, and trade-in — then computes your payment and a month-by-month amortization schedule.

How it's calculated

Loan amount  P = price + price × tax% ÷ 100 − down payment − trade-in
Monthly rate r = APR ÷ 1200,  n = months
Payment      M = P × r × (1 + r)^n ÷ ((1 + r)^n − 1)
Total interest = M × n − P

For example, financing $30,000 at 6% APR over 60 months gives a payment of $579.98 and about $4,799 of total interest. Stretching the same loan to 84 months drops the payment but raises the lifetime interest cost substantially — that trade-off is the most important number on this page.

A note on trade-ins and tax: many states (including Texas, Florida, and most others) only charge sales tax on the price minus your trade-in value, which lowers the tax bill. A handful of states — notably California — tax the full price regardless of trade-in. For simplicity, this tool taxes the full vehicle price, so in trade-in-credit states your real tax (and loan amount) may be slightly lower than shown. Set the tax slider to 0 and add tax yourself if you want full control.

Other assumptions and limitations: documentation fees, title, registration, extended warranties, and GAP insurance are excluded — these are often rolled into the loan at the dealership and would raise the financed amount. APR is assumed fixed for the life of the loan, which is standard for US auto loans. The calculator also assumes your down payment and trade-in together don't exceed the price plus tax; if they do, the loan amount floors at $0.

A common affordability rule of thumb is 20/4/10: put at least 20% down, finance for no more than 4 years, and keep total vehicle costs under 10% of gross income.