Auto Loan Calculator
Free auto loan calculator with US state sales tax, trade-in credit, negative equity rollover, and full amortization. Solves for monthly payment or affordable price.
Frequently asked questions
How is a monthly car payment calculated?
The monthly payment is computed with the standard amortization formula M = P·r(1+r)^n / ((1+r)^n − 1), where P is the amount financed, r is the APR divided by 12, and n is the loan term in months. Amount financed equals the sale price plus rolled-in taxes and fees, minus down payment, cash incentives, and net trade-in equity.
How is sales tax calculated on a car?
Most US states charge sales tax on the vehicle price minus the trade-in value (the "trade-in credit"). A minority of states — California, Hawaii, Kentucky, Maryland, Virginia, and DC — tax the full sale price regardless of trade-in. This calculator applies the correct rule automatically based on the state you select.
Should I roll negative equity into a new auto loan?
Rolling negative equity — the amount you owe on your trade above what it is worth — into a new loan means you start the new loan already underwater. It is usually cheaper to pay off the old loan first, delay the purchase, or make a larger down payment. This calculator adds any negative equity into the financed amount so you can see the true monthly cost before signing.
Does a trade-in reduce sales tax?
In most states, yes — you only pay sales tax on the price after the trade-in value is subtracted, which can save hundreds or thousands of dollars. The exceptions are California, Hawaii, Kentucky, Maryland, Virginia, and DC, where sales tax is charged on the full price. The state tax table tab shows every state.
60-month vs 72-month auto loan — which is better?
A 72-month loan lowers the monthly payment but adds one to two percentage points to typical APRs and roughly 20-30% more total interest over the life of the loan. It also keeps you underwater on the vehicle for longer. A 60-month loan is the sweet spot for most buyers who plan to keep the car more than four years.
How much car can I afford?
A common rule is to keep the total car payment (loan + insurance + fuel + maintenance) under 15% of take-home pay, with a down payment of at least 20% and a loan term of 60 months or less. Switch this calculator to "Monthly → Affordable Price" mode to back-solve the maximum vehicle price from your target monthly payment.