The real monthly payment on that car — trade-in, sales tax and all — before you're sitting in the finance office.
Dealers sell payments, not prices. Stretching a $35,000 loan at 7% from 60 to 72 months drops the payment from about $693 to $597 — feels great — but you pay roughly $1,400 more in interest, and at 84 months it's about $2,800 more. Longer terms also mean more years owing more than the car is worth.
Sales tax and your trade-in: in most states you only pay tax on the price minus your trade-in — that's how this calculator works. A handful of states (California is the big one) tax the full price with no trade-in credit, so set your trade-in's tax effect accordingly and check your state's DMV page. We also assume tax is rolled into the loan, which is what most buyers do.
The cleanest negotiating move: settle the vehicle price first, then the trade-in, then financing — three separate conversations, so a "great" number in one can't hide a bad one in another.
Estimates are for education, not financial advice. Your lender's exact numbers may differ slightly.
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Financing a car uses the same amortization math as a mortgage, applied to a smaller balance over a shorter term. We start from the vehicle price, add sales tax, subtract your down payment and trade-in value, and finance the rest at your rate over the number of months you choose. The result is your monthly payment plus the total interest you'll pay — the number dealers rarely put in front of you, because stretching the term lowers the monthly payment while quietly raising the total cost.
Take a $35,000 car with $3,000 down and a $5,000 trade-in, financing about $27,000 (plus tax) at 7%. Over 60 months that's roughly $535 a month and about $5,000 in total interest. Stretch it to 72 months and the payment drops to around $460 — but you'll pay closer to $6,000 in interest and spend an extra year in debt. Push to 84 months and you risk owing more than the car is worth for much of the loan. The calculator makes that trade visible so a lower monthly number doesn't hide a bigger total.
Does it include sales tax and fees?
It includes sales tax on the purchase. Registration, documentation, and dealer fees vary by state and dealer — add them to the price if you want to be precise.
How does a trade-in help?
Your trade-in value (minus any loan still owed on it) works like extra down payment, shrinking the amount you finance and the interest you pay. In many states it also reduces the taxable price.
Is a 72- or 84-month loan a bad idea?
Not always, but longer terms mean more total interest and a longer stretch of being "upside down" — owing more than the car's worth. If you need the long term just to afford the payment, it's often a sign to look at a cheaper car.
Should I put money down?
A down payment lowers your balance, your interest, and your risk of going upside down. Even a modest amount noticeably improves the numbers above.