Enter the vehicle price, your down payment and trade-in, your state’s sales tax, and the loan’s rate and term — you’ll see the estimated monthly payment instantly, along with the numbers dealers rarely volunteer: the total interest and the loan’s true total cost. Free, no signup, and every calculation runs in your browser.
How to use this calculator
- Vehicle price — the negotiated price of the car, not the sticker.
- Down payment — cash you’ll pay upfront.
- Trade-in value — what the dealer credits for your current car.
- Sales tax — your combined state and local rate; it’s applied to the price minus your trade-in.
- Interest rate — the APR you’ve been quoted.
- Term — the loan length in months; 36–84 are typical.
The result updates as you type, and the address bar updates too — copy the URL to save or share a scenario.
How the trade-in cuts your sales tax
In most US states, tax is charged on the price minus the trade-in credit. On a $30,000 car with a $5,000 trade-in at 8%, you’re taxed on $25,000 — that’s $2,000 instead of $2,400, so the trade-in is worth $400 more than its face value. This calculator uses that convention, and it’s stated in the methodology below so you can check the math. A handful of states tax the full price before the credit; if yours does, enter the trade-in amount in the down payment field instead — the amount financed stays correct and the tax follows your state’s rule.
Longer terms look cheaper — until you add them up
The monthly payment is the number on the dealer’s four-square worksheet, and stretching the term is the easiest way to make it look small. Run $35,000 financed at 7% through the calculator both ways: at 60 months the payment is about $693 with roughly $6,600 of total interest; at 84 months it drops to about $528 — but total interest climbs to roughly $9,400. That $165 of monthly relief costs about $2,800 extra, and because cars depreciate fastest in the first years, an 84-month loan leaves you owing more than the car is worth for longer. A useful habit: choose the term by total cost, then adjust the down payment until the monthly figure fits your budget — a pre-approval from a bank or credit union before you visit the dealership gives you a real APR to plug in here and a baseline to compare against dealer financing. If high-interest card debt is competing for the same dollars, check the credit card payoff calculator first — card APRs usually dwarf auto rates.
Limits
This is the loan’s core cost, not the full deal. Documentation, title, and registration fees aren’t modeled — add them to the price field if you’ll finance them. The tax field is a single combined rate, and state rules differ (some cap the trade-in credit or tax the full price). The math assumes a fixed rate with no extra payments, and the APR you enter should be the lender’s quoted APR, which can include fees beyond the note rate. Rolling negative equity from an old loan into the new one? Add that balance to the vehicle price to see its real effect.
The same annuity formula powers our mortgage payment calculator if you’re comparing bigger borrowing decisions. Browse all our calculators — each shows its formula and sources — and our file tools, which run privately in your browser too.