Auto Loan Calculator

How to use this calculator

Enter the vehicle price — the sticker price you have agreed with the dealer or private seller. Add your down payment (cash you pay up front) and the trade-in value the dealer credits for your old car. Set your local sales tax rate, the interest rate (APR) on the loan, and the term in months. The result updates instantly so you can test different scenarios and see exactly what each lever does to your monthly payment.

How this is calculated

First we work out the taxable amount. In most US states the trade-in value is deducted before tax, so the sales tax applies to the price minus your trade-in. Next we add that tax to the price and subtract your down payment and trade-in to get the amount financed — the loan principal. We then apply the standard amortization formula using a monthly rate (your APR divided by 12) over the number of months in your term. Total interest is every payment added up minus the amount financed, and total cost is your down payment plus all the payments you will make.

Educational estimate, not financial advice — see our disclaimer.

A worked example

Say you are buying a car for $35,000 with a $5,000 down payment and no trade-in, in a state with 7% sales tax, at a 7% APR over 60 months. Sales tax on the full price is $2,450, bringing the amount financed to $35,000 + $2,450 − $5,000 = $32,450. At 7% over 60 months that works out to about $642 a month. Across the loan you pay roughly $6,090 in interest, so the total cost — down payment plus every payment — lands near $43,540. Add a $4,000 trade-in to that same deal and your taxable amount drops, the loan shrinks, and the monthly payment falls by around $80.

Tips for a cheaper car loan

• Shop financing separately from the car. Get a pre-approval from your bank or credit union before you set foot in the dealership. That gives you a benchmark APR to beat and stops the dealer from being your only option.
• Put more down. A bigger down payment cuts the amount financed dollar for dollar, lowers your monthly payment, and reduces the total interest you pay over the life of the loan.
• Keep the term short. A 72- or 84-month loan looks tempting because the monthly figure is small, but you pay far more interest and risk owing more than the car is worth.
• Mind your credit score. The single biggest driver of your rate is your credit. A few months of on-time payments before you shop can move you into a better rate tier.

Curious how the same math applies to other borrowing? Our general loan calculator handles personal loans, and the debt-to-income calculator shows whether a new car payment fits your budget.