Auto Loan Calculator
Your real monthly car payment — with sales tax, trade-in and fees included.
The sticker price is never what a financed car really costs. Sales tax and fees get rolled into the loan, and interest then accrues on all of it — this calculator shows the full chain: amount financed, total interest, and the true total cost including your down payment and trade-in.
How to use
- Enter the vehicle price, your down payment and any trade-in value.
- Add your local sales tax rate and dealer/title fees — these are usually financed too.
- Set the APR and term, then click "Calculate payment".
- Try a shorter term: the monthly payment rises, but total interest falls fast.
About this tool
Sales tax here is calculated on the price minus your trade-in value, which is how most US states do it; a few states tax the full price. If yours is one of them, set the trade-in to 0 in the tax sense by raising the tax rate proportionally — or simply treat the result as a close estimate.
Everything runs in your browser. The numbers you enter are never sent anywhere.
How it works
The amount financed is price + sales tax + fees − down payment − trade-in, where sales tax applies to (price − trade-in) in most states. The monthly payment then uses the standard amortization formula: payment = L × R / (1 − (1 + R)^−N), with L the amount financed, R the monthly rate (APR ÷ 12) and N the number of monthly payments.
Total interest is simply (payment × N) − L, and the total cost of the car adds back what you paid up front: down payment + trade-in + all payments. That total — not the sticker price — is the honest number to compare between deals.
Worked examples
$30,000 car, $3,000 down, 8% tax, 6% APR, 60 months: Tax on $30,000 is $2,400, so the amount financed is 30,000 + 2,400 − 3,000 = $29,400. At 6% APR over 60 months the payment is $568.38, total interest $4,703.06, and the true total cost is $37,103.06.
Frequently asked questions
Why is my amount financed higher than the price minus down payment?
Because sales tax and fees are added to the amount you borrow. On a $35,000 car at 8% tax, that is roughly $2,400–$2,800 extra financed before interest even starts.
Is a longer term ever a good idea?
It lowers the monthly payment, which can help cash flow, but you pay much more interest and risk owing more than the car is worth (being "upside down") for the first years. Shorter terms cost less overall.
Does the trade-in really reduce sales tax?
In most states, yes — you are taxed on the price difference. A handful of states tax the full price regardless. The calculator follows the majority rule; check your state if the figure matters to the dollar.
Is my data sent anywhere?
No. Every calculation runs in your browser. Nothing you type ever leaves your device.
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