Auto Loan Calculator — Car Payment, Interest & Total Cost
Enter the vehicle price, your down payment and trade-in, the sales tax and fees, plus the interest rate and term. CalcWize rolls tax and fees into the amount financed, then returns the monthly payment, the total interest you will pay, and the full cost of the loan.
When this is useful
Comparing finance offers, checking a dealer’s monthly-payment quote against the real numbers, or seeing how a bigger deposit or a shorter term changes what you pay. Dealers love to negotiate on the monthly payment — this shows the price and interest hiding behind it.
How the payment is worked out
CalcWize uses standard amortising-loan math on the amount financed (price + sales tax + fees − down payment − trade-in). Each month, interest is charged on the outstanding balance and the rest of the payment reduces principal, so a longer term means more payments and considerably more interest.
Watch the term, not just the payment
A lower monthly payment usually means a longer loan and more total interest. Stretching a loan to 72 or 84 months makes the payment look affordable while quietly adding thousands in interest — and you stay underwater (owing more than the car is worth) for much longer. Shorter is cheaper.
Sales tax and fees
In many places, tax and documentation or registration fees are financed alongside the car, so you pay interest on them too. CalcWize includes them in the amount financed; set sales tax to 0 if it does not apply where you are or is paid separately.
Common mistakes
Focusing only on the monthly payment, ignoring the APR (which folds in most fees), and rolling negative equity from an old loan into the new one. Always ask for the APR and the total of payments — not just the monthly figure — before you sign.
Frequently asked questions
- Does a longer loan really cost that much more?
- Yes. Stretching from 48 to 72 months lowers the monthly payment but can add thousands in interest, because you’re borrowing more for longer. It also keeps you underwater — owing more than the car is worth — well into the loan.
- What’s the difference between APR and interest rate?
- The interest rate is the cost of borrowing the principal; the APR also includes most mandatory fees, so it’s the better figure for comparing offers. Always ask a lender for the APR.
- Should I roll tax and fees into the loan?
- You can, and the calculator models it, but you then pay interest on them too. Paying tax and fees in cash up front keeps both the amount financed and the interest lower.
How we calculate it
The amount financed is the price plus sales tax and fees, minus your down payment and trade-in. The monthly payment uses the standard amortising formula: payment = financed × r(1 + r)ⁿ ÷ ((1 + r)ⁿ − 1), where r is the monthly rate and n the number of payments. Total interest is the sum of payments minus the amount financed.
What it doesn't do
- Lease agreements (use the Lease vs Buy calculator)
- How much car to buy in the first place (use Car Affordability)
- Balloon or PCP-style finance with a large final payment
Last reviewed: 2026-05