Auto Loan Calculator
Calculate your full auto loan payment including sales tax, fees, trade-in value and any down payment — and see the total interest over the life of the loan.
How to use the Auto Loan Calculator
- Enter your inputs into the Auto Loan Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
The auto loan payment formula
M = P · r(1 + r)^n / ((1 + r)^n − 1), where P = price + tax + fees − down − trade
The financed principal P is the vehicle price plus sales tax and fees, minus the down payment and trade-in. The same amortization formula then gives the fixed monthly payment over the loan term in months.
Worked example
A $32,000 car with $2,000 in tax and fees, $4,000 trade-in and $3,000 down gives P = $27,000. At 7.5% APR over 60 months: M ≈ $541.07. Total paid: about $32,464 — roughly $5,464 in interest.
Frequently asked questions
Should I include sales tax in the financed amount?
In most US states, sales tax can be rolled into the loan. Doing so raises the monthly payment and total interest; paying tax in cash at signing keeps the loan smaller.
How does a trade-in affect my loan?
Trade-in value reduces the financed principal dollar-for-dollar, lowering both monthly payment and total interest. If you owe more on your trade than it is worth, the negative equity gets added to the new loan.
What auto loan term is best?
Shorter terms (36–48 months) have higher payments but much less total interest. 72- and 84-month loans lower the payment but often leave you underwater for years.
Does my credit score affect the rate?
Significantly. The gap between top-tier and subprime auto rates is often 8–15 percentage points, which can double the lifetime interest on the same loan.