The sticker price is only one line of a car deal. Rebates, your trade-in, the loan still owed on it, sales tax and a stack of fees all feed into the amount you actually borrow — and small changes in those lines move the monthly payment more than people expect. This calculator builds the amount financed line by line the way a dealer’s buyer’s order does, then turns it into a payment and a full schedule.
How to use the auto loan payment calculator
- Enter the vehicle price, any cash rebates or incentives and your cash down payment.
- Enter your trade-in value and how much you still owe on that car, if anything.
- Enter your sales tax rate and the total of title, registration and dealer fees. Choose whether the trade-in and rebates reduce the taxable price in your state, and whether tax and fees are financed or paid in cash.
- Enter the APR and term, and optionally the first payment date.
- Check the “How the amount financed is built” table, then the payment, out-the-door price and schedule.
Auto loan formulas
In the payment formula, P is the amount financed, r the APR ÷ 12 and n the term in months. If tax and fees are paid at signing instead, they leave the amount financed and join your cash due.
Worked example
A $35,000 vehicle with a $1,000 rebate, $3,000 down and an $8,000 trade-in with $2,000 still owed. Sales tax is 7%, fees are $800, and the loan is 6.9% for 60 months.
Taxable price: 35,000 − 8,000 = $27,000; sales tax = $1,890
Net trade-in: 8,000 − 2,000 = $6,000
Amount financed: 35,000 − 1,000 − 3,000 − 6,000 + 1,890 + 800 = $27,690
Payment: $546.99 a month; total interest $5,129.38
Out-the-door price: 35,000 − 1,000 + 1,890 + 800 = $36,690
If the state taxed the full $35,000 instead, tax would be $2,450 and the payment would rise to $558.05.
The lines that change your payment most
| Change from the example | New payment |
|---|---|
| None | $546.99 |
| No trade-in tax credit | $558.05 |
| Owing $11,000 on the trade-in instead of $2,000 | $724.78 |
Negative equity
Rolling an underwater trade-in into a new loan is one of the costliest moves in car buying. In the third row, $3,000 of old debt is added to the new loan, the amount financed jumps to $36,690 and the payment rises by about $178. You also start the new loan owing more than the new car is worth.
Fees worth questioning
Government charges such as title and registration are fixed, but documentation fees, dealer add-ons, paint protection and extended warranties are negotiable. Ask for an itemized out-the-door quote before discussing monthly payments.
Financing vs. paying tax and fees up front
Paying tax and fees in cash lowers the amount financed and the interest you pay on it. Financing them preserves cash but means borrowing for costs that add no value to the car.
For a quick payment without the deal details, use the car loan calculator. To work backward from a budget, try how much car can I afford.
Estimates only. Tax treatment of trade-ins, rebates and fees differs by state and locality; your retail installment contract shows the official figures.
Frequently asked questions
How do I calculate a car payment with a trade-in and sales tax?
Start with the price, subtract rebates, your cash down payment and the trade-in's net value (trade-in value minus what you still owe on it), then add sales tax and fees if you are financing them. That is the amount financed. Apply the loan formula with your APR and term to get the payment.
Does a trade-in reduce sales tax?
In most US states, yes: sales tax is charged on the price minus the trade-in allowance, which can be worth hundreds of dollars. A handful of states tax the full price regardless of the trade. In the example on this page, the trade-in credit saves $560 of tax.
What is negative equity on a trade-in?
It is when you owe more on your current car than it is worth. The difference does not disappear — the dealer pays off your old loan and adds the shortfall to your new one, so you pay interest on a car you no longer own.
Are rebates taxed?
It depends on the state and the type of incentive. Many states tax the price before manufacturer rebates, while dealer discounts usually reduce the taxable price. Tick the rebate box only if your state allows the deduction.
What is the out-the-door price?
It is the total you pay for the vehicle itself, including taxes and fees but before financing: price minus rebates, plus sales tax, title, registration and dealer fees. Negotiating on the out-the-door price prevents fees from being added late in the deal.