US Auto Loan Calculator

This calculator turns a few details about your car purchase into a monthly payment, so you can see what a loan would cost before you sign. It works for any US auto loan with a fixed APR.

Start with the vehicle price, the negotiated price of the car before tax. Then enter your down payment, the cash you are paying up front, and your trade in value, the amount a dealer credits you for your old vehicle. Both reduce the amount you need to borrow.

Enter your sales tax rate as the combined state and local rate for where you register the car. There is no single national rate in the US, so check your own city and county rate. Add your loan APR as the annual rate your lender quotes, and the loan term as the number of months, for example 60 for a five year loan.

The results update instantly as you type. Try a larger down payment, a different term, or a lower APR to see how each one changes your monthly payment and the total interest you would pay over the life of the loan.

The calculator first works out the amount financed. It charges sales tax on the full vehicle price, so the sales tax equals the price multiplied by the tax rate divided by one hundred. The amount financed is then the price plus that sales tax, minus your down payment and your trade in value. If that figure would be negative, it is set to zero, because you cannot borrow a negative amount.

It then applies the standard amortising loan formula to find the level monthly payment. In words: the payment equals the amount financed multiplied by the monthly interest rate, divided by one minus the quantity one plus the monthly rate raised to the power of minus the number of months. The monthly rate is the APR divided by one hundred and then by twelve. When the APR is zero, the payment is simply the amount financed divided by the number of months.

From the monthly payment it derives the rest. The total of payments is the monthly payment multiplied by the number of months. The total interest is the total of payments minus the amount financed, which is the extra you pay for borrowing. The total cost including tax is the vehicle price plus the sales tax plus the total interest, the full price of owning the car through the loan.

Every figure assumes a fixed APR and equal monthly payments across the term, which is how most US auto loans are structured. It does not model variable rates, balloon payments or skipped months.

The headline figure is your monthly payment, the amount of principal and interest you would pay each month. This is the number most buyers compare against their budget, but it is worth looking past it to the total cost as well.

The amount financed shows how much you are actually borrowing after your down payment and trade in. A bigger down payment or trade in lowers this figure, which lowers both the monthly payment and the total interest. The sales tax figure shows the tax added to the deal, which can be a significant sum on a higher priced vehicle.

The total interest is the price of borrowing over the whole term. A longer term lowers the monthly payment but raises this number, so a cheaper monthly payment is not always the cheaper deal. The total cost including tax brings everything together: the car, the tax and the interest, so you can see the real price of the purchase.

Remember these are estimates. They exclude registration, title and documentation fees, gap insurance and your ongoing car insurance, all of which vary by state and lender. Some states also tax the price after a trade in rather than the full price, so adjust the price you enter if that applies to you. Treat the output as a planning guide rather than a quote, and not as financial advice.