What is the Auto Loan Calculator?
The Auto Loan Calculator estimates your true monthly payment and total cost of financing a vehicle, rolling in sales tax, dealer fees and any trade-in value — not just the sticker price and the advertised APR.
How to Use This Calculator
- Enter the negotiated vehicle price (not the sticker price).
- Add your down payment and any trade-in value. Both reduce the amount you finance; the trade-in also reduces the taxable amount.
- Enter your state/local sales-tax rate and any dealer fees for title, documentation and registration.
- Pick a loan term and enter the APR from your lender or pre-approval.
- Review the results. You get the monthly payment, the amount financed, total interest, and total cash cost (down payment plus every scheduled payment). The doughnut chart splits that total cash cost into the car, taxes, fees, and interest.
How does the underlying math work?
First the amount financed is assembled:
Then the monthly payment uses the same amortizing-loan formula as a mortgage:
- i — monthly rate = APR ÷ 12
- n — number of monthly payments (the term)
Total interest is (M × n) − Financed, and total cash cost is DownPayment + (M × n).
Real-world practical application
Shoppers use it to compare dealer financing against a credit-union pre-approval, to see how a 72- or 84-month term quietly inflates total interest compared with a 60-month term, and to check whether a trade-in is worth more toward the purchase price or sold privately.
Frequently Asked Questions
How long should my auto loan be?
Shorter is cheaper. A common guideline is to finance a car for no more than 60 months. Terms of 72 or 84 months shrink the monthly payment but add a lot of interest, and you are likely to be "upside down" — owing more than the car is worth — for years.
Does a trade-in reduce the sales tax I pay?
In most U.S. states, yes: tax is charged on the new vehicle's price minus the trade-in allowance. A handful of states tax the full price. This calculator uses the more common price-minus-trade-in method.
What APR can I expect on a car loan?
Rate depends mostly on your credit score, the term, and whether the vehicle is new or used. Strong credit can mean single-digit rates on a new car; subprime borrowers may pay 15% or more. Getting pre-approved by a bank or credit union first gives you a benchmark to negotiate against.
Related Calculators
- Debt Payoff Timeframe — model paying the loan off faster.
- Mortgage Calculator — the same amortization math for a home.
- Real ROI — the opportunity cost of a big down payment vs. investing it.