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Auto Loan Calculator

An auto loan calculator estimates the monthly payment, total interest, and amount financed on a car loan. Enter the price, down payment, trade-in value, sales tax, rate, and term.

By the Personalloaned Editorial Team · Last updated 2026-09-16

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Method

How this calculator works

An auto loan is secured by the vehicle. The amount financed is the price, minus your down payment and trade-in credit, plus any sales tax on the difference.

Amount financed = price - down payment - trade-in + sales tax, where sales tax = (price - trade-in) * tax rate.

Then M = P * r * (1 + r)^n / ((1 + r)^n - 1).

  • P = amount financed
  • r = monthly rate = annual rate / 12 / 100
  • n = number of monthly payments

If the down payment and trade-in cover the price and tax, nothing is financed and the payment is 0.

Sales tax rules vary by state and locality, and auto loan rates vary with credit and term. Enter your own figures.

Common questions

Frequently asked questions

Is sales tax always financed?
Not always. Some buyers pay tax up front. If you finance it, add it to the amount financed as this calculator does; if you pay it separately, set the tax rate to 0.
What if my down payment and trade-in exceed the price?
Then the amount financed is 0 and the monthly payment is 0. You would not need a loan in that case.
How does the term affect my auto loan?
A longer term lowers the monthly payment but increases total interest. It can also mean owing more than the car is worth for longer.
Are auto loan rates fixed or variable?
Many auto loans are fixed-rate, but some are variable. This calculator assumes a fixed rate for the whole term.

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