Auto Loan Calculator

The financed amount is what the payment is built on, so the order of operations matters: tax and fees are added to the price, then your cash and trade come off the total.

• Sales tax = (vehicle price − trade-in) × tax rate ÷ 100
• Out-the-door price = vehicle price + sales tax + fees
• Amount financed = out-the-door price − down payment − trade-in (never below $0)
• Monthly rate r = APR ÷ 100 ÷ 12, payments n = term in months
• Payment = financed × r ÷ (1 − (1 + r)^−n); at 0% APR it is financed ÷ n
• Total interest = payment × n − financed

The amount financed — not the sticker price — is what your payment is built on. Total cost of the vehicle adds your cash and trade-in back on top of what the loan repays.

Common mistakes and assumptions

• Assuming the tax basis matches your state. This calculator taxes the price minus the trade-in; some places tax the full price.
• Double-counting the trade-in as a down payment. Enter each in its own field.
• Stretching the term to hit a payment: the payment falls but total interest rises.

A $32,000 vehicle with $3,000 down, a $6,000 trade-in, 6.5% sales tax, $600 in fees, financed at 7.25% for 60 months.

1. 1Taxable base = $32,000 − $6,000 = $26,000, so sales tax = $1,690.
2. 2Out-the-door = $32,000 + $1,690 + $600 = $34,290.
3. 3Amount financed = $34,290 − $3,000 − $6,000 = $25,290.
4. 4Monthly rate = 7.25 ÷ 1200 = 0.00604167 over 60 payments gives a payment of $503.76.
5. 5Total interest = $503.76 × 60 − $25,290 = $4,935.64.

How is sales tax handled?

It is charged on the vehicle price minus your trade-in allowance, which is the most common US rule. Some states tax the full price with no trade credit; in that case leave the rate at 0 and enter the dollar tax under fees.

What if I owe more than my trade is worth?

Enter 0 as the trade-in value and add the negative equity to the fees field. That rolls the shortfall into the financed amount, which is what a dealer would do.

Does this include an extended warranty or gap insurance?

Only if you add them to the fees field. Dealer add-ons are financed just like the vehicle, so they raise both the payment and the interest you pay.

Is a longer term cheaper?

The monthly payment is lower, but the total interest is higher and you stay underwater longer. Compare the total interest line across terms, not just the payment.