An auto loan calculator tells you what a car really costs before you sign anything. The sticker price is only the start: sales tax, title and registration fees, your down payment, and the trade-in on your old car all change the amount you actually finance — and the interest rate and term decide what that loan costs you in the end.
Consider a $35,000 car with $5,000 down, a $4,000 trade-in, 7% sales tax and a 60-month loan at 7.9% APR. The payment comes out around $580 a month — with about $6,100 in interest over the life of the loan. Stretch that to 84 months and the payment drops to roughly $445, but total interest climbs past $8,700. Running the numbers first is what keeps you from that surprise.
This calculator uses the same amortization math lenders use: your amount financed equals price minus down payment minus trade-in, plus sales tax (on price minus trade-in, the credit most US states allow) and fees.
How to use the Auto Loan Calculator
- Enter the vehicle price — the out-the-door number before taxes and fees.
- Add your down payment and trade-in value. Both reduce the amount you need to borrow.
- Set your sales tax rate and fees. Tax is applied to the price after trade-in credit; fees are added to the financed amount.
- Enter the APR from your lender or dealer quote and choose the term, then click Calculate payment.
- Compare terms: try 48, 60 and 72 months to see how the payment trades off against total interest.
Tips for accurate results
- Get pre-approved by a bank or credit union before visiting the dealer — their rate is your negotiating baseline.
- A shorter term almost always beats a lower monthly payment: 60 months is a good balance for most buyers.
- Keep the total monthly payment (loan + insurance + fuel) under about 15% of your take-home pay.
Frequently asked questions
How is a monthly auto loan payment calculated?
Lenders use the amortization formula M = P·r(1+r)ⁿ / ((1+r)ⁿ−1), where P is the amount financed, r the monthly interest rate (APR ÷ 12), and n the number of monthly payments. This calculator applies exactly that formula.
Is sales tax included in the auto loan estimate?
Yes — your sales tax rate is applied to the price minus trade-in value (the credit most US states allow), and title/registration fees are added to the amount financed. A few states tax differently, so the dealer's final number may vary slightly.
Is a longer car loan term better?
A longer term (72 or 84 months) lowers the payment but raises total interest — and you're still paying after the car has depreciated. A 48- to 60-month term suits most buyers.
How much should I put down on a car?
Aim for at least 10–20% of the price. A larger down payment shrinks the loan and interest, and keeps you from owing more than the car is worth as it depreciates.