Auto Loan Calculator
Estimate your monthly car payment including sales tax, down payment, and trade-in value.
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
This tool provides general financial estimates for educational purposes only and is not personalized financial, tax, or investment advice. Consult a licensed financial professional before making major financial decisions.
About the Auto Loan Calculator
The auto loan calculator shows what a car will really cost per month once sales tax, your down payment and any trade-in are taken into account. Dealers often quote a monthly figure first and the price second; working the other way round — price, tax, deposit, then payment — puts you back in control of the negotiation. The tool adds sales tax to the vehicle price, subtracts your down payment and trade-in to get the amount financed, and then amortizes that balance over the term you choose using the standard fixed-payment loan formula. Alongside the monthly payment it reports the total interest, so you can see how much a longer term really costs. Use it before visiting a dealer, when comparing a bank pre-approval with dealer financing, or when deciding whether a bigger deposit is worth it.
How to use it
- 1Enter the agreed vehicle price before tax.
- 2Add your cash down payment and the value of any trade-in.
- 3Enter your local sales tax rate as a percentage.
- 4Enter the annual interest rate (APR) you were quoted and the term in months.
- 5Press Calculate to see the amount financed, monthly payment and total interest.
Worked example
a $30,000 car with 7% sales tax adds $2,100 in tax. After a $3,000 down payment the amount financed is $29,100. At 6.5% for 60 months the payment is about $569 a month and total interest is about $5,062. Stretching the same loan to 72 months lowers the payment but increases the interest you pay.
How it works
How it works
The amount financed equals the vehicle price plus sales tax, minus your down payment and trade-in. That balance is amortized over the loan term.
Formula
Payment = P × r / (1 − (1+r)⁻ⁿ)
Who it is for
Car buyers comparing dealer offers, people deciding between a 48-, 60- or 72-month term, and anyone checking whether a payment fits their monthly budget.
Why it helps
It separates the price of the car from the cost of borrowing, which is where most of the hidden expense in a car deal sits.
Common use cases
- Checking a dealer’s quoted monthly payment against the agreed price
- Comparing a bank or credit-union pre-approval with dealer financing
- Seeing how much a larger down payment or trade-in lowers the payment
- Comparing the total interest on a 48-month and a 72-month term
Tips for better results
- Negotiate the vehicle price first, then discuss financing.
- Ask for the APR, not just the monthly payment, when comparing offers.
- Check whether your state taxes the full price or the price after trade-in, and adjust the tax figure if needed.
Common mistakes to avoid
- Judging a deal by the monthly payment alone while the term quietly gets longer.
- Forgetting registration, documentation and dealer fees, which this calculator does not include.
- Entering the interest rate as a decimal (0.065) instead of a percentage (6.5).
Frequently asked questions
A:This calculator adds sales tax to the amount financed, which is common in many states.
A:Yes — it lowers the amount financed, reducing both your monthly payment and total interest.
A:Shorter terms mean higher payments but far less total interest. 48–60 months is typical.
Reviewed for accuracy · Last updated October 7, 2026
Formulas follow standard amortization, present/future value, and compounding mathematics used throughout the financial industry, and are periodically checked against reference calculations.
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards
References & sources
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