Tool · Investor Sam Auto

Auto Loan Payment Calculator

June 30, 2026 • By the Investor Sam Editorial Team • Reviewed by Berly Sam Varghese, Editor
Before you sign at the dealership, you want one number in your pocket: what this car actually costs per month, and what it costs in total once interest is added. This calculator takes the vehicle price, your down payment and trade-in, sales tax, the loan rate, and the term, then returns the monthly payment plus the total interest you will pay over the life of the loan. Knowing the amount financed and total interest up front is the single best defense against a longer term quietly inflating the price.

Example: Vehicle price: 35000 $ · Down payment: 4000 $ · Trade-in value: 0 $ · Sales tax: 6 % · Loan APR: 7.5 % · Loan term: 60 months

Monthly payment$663
Total interest paid$6,695
Amount financed$33,100
Total cost of the car$43,795

Worked example

Take a $35,000 car with $4,000 down and 6% sales tax. Tax adds $2,100, so you finance $35,000 + $2,100 - $4,000 = $33,100. At 7.5% APR over 60 months, that works out to a monthly payment of about $663. Over the full term you pay roughly $6,680 in interest, so the car that stickered at $35,000 costs you about $43,780 all in once tax and interest are counted.

Frequently asked questions

Why is the amount financed higher than the price minus my down payment?

Sales tax is usually rolled into the loan, so it is added to the price before your down payment and trade-in are subtracted. That is why the financed amount can be larger than you expect. Enter your state and local combined rate to see the real figure.

Does a longer term really cost more?

Yes. A 72- or 84-month loan lowers the monthly payment but you pay interest for more years, so the total interest and total cost rise. Run the tool at 60 and 72 months to see exactly how much a lower payment costs you overall.

How much should I put down?

A common guideline is at least 20% down on a new car so you are not immediately underwater as it depreciates. A larger down payment shrinks the amount financed and every downstream number, including total interest.

Is the total cost the price I really pay?

This total includes price, sales tax and interest. It does not include ongoing costs like insurance, fuel and maintenance. For the full picture, pair this with a true-cost-of-ownership calculator.

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Sources

Berly Sam Varghese · Editor, Investor Sam

Berly Sam Varghese is an engineer who treats money the way he treats any hard problem — something to be engineered, not gambled on. He funded years of education and built real financial stability the patient way, by living below his means and investing rather than borrowing. He writes for the person trying to make a car decision without overpaying for years. He reviews and approves every article on Investor Sam and checks the figures against primary sources before anything is published. More about our standards.