What this calculator does
An auto loan amortizes a fixed principal over a fixed term at a stated annual percentage rate (APR). Each monthly payment covers interest on the remaining balance first; the rest reduces principal. This tool estimates the amount financed after down payment, trade-in and a simple sales-tax add-on, then shows the payment, total interest and the first year of amortization (plus the final row).
Shop the out-the-door price and the APR separately. Dealers sometimes quote a low monthly payment by stretching the term or packing products into the amount financed. Use this calculator to reverse-engineer what a quoted payment implies, and compare it with a credit-union or bank preapproval.
Amount financed
We treat amount financed as price + estimated tax + fees − down payment − trade-in. Some states tax the full price; others tax price minus trade. Documentary fees, title and registration may be cash or financed — put financed items in the fees box. Negative equity from a prior loan rolled into a new deal increases the amount financed and is one of the fastest ways to become underwater.
APR, term and total interest
Longer terms cut the monthly payment but usually raise total interest and keep you underwater longer. A 72- or 84-month loan can look affordable until you compare total interest with a 48- or 60-month option at a similar APR. See our guide on how auto loan APR works and reading a loan offer.
How to use this tool
Enter realistic numbers from quotes, your current loan statement or a dealer worksheet — not round guesses when precision matters. Results update as you type and stay in your browser; nothing is uploaded to our servers. Screenshot or write down the output with the date so you can compare later.
Change one input at a time when you are comparing scenarios. That makes cause and effect obvious. If you share the result with a partner or credit-union loan officer, share the inputs too so nobody debates a black-box number.
This page is general information and arithmetic, not personalised credit advice. Rates, fees, tax rules and dealer programs change. When an official source or your contract disagrees with text here, trust the contract and the official source, and tell us via the contact page so we can fix the page.
What the numbers mean
Read every label carefully. APR is not the same as a money factor. Cap cost is not the same as MSRP. A residual percentage is a contractual estimate of end-of-lease value, not a promise of what a buyer would pay you for a car you own. Amortization schedules round differently across lenders.
Use related guides on this site for the “why” behind the math. Sister sites on dollarfinch.com cover other money jobs — for example paycheck withholding on Take-Home Clarity, cash parking on CashLadder, and year-end tax moves on Year-End Moves. AutoLane stays focused on vehicle financing arithmetic.
Advertisers help keep the tools free. Ads are labelled. Affiliate links, when present, are disclosed on the page and in the affiliate disclosure. Commissions never change the calculator formulas.
Good habits before you sign
Get a prequalification or preapproval from a bank or credit union before you visit a dealer so you have an independent APR to compare. Ask for the out-the-door price before talking about monthly payments. Read every add-on (extended warranty, GAP, paint protection) as an optional product with a price — not as a required line.
Do not paste Social Security numbers, full account numbers or passwords into any web form, including ours. We do not ask for them. For refinance shopping, you can usually prequalify with soft-pull tools from lenders; confirm how each lender checks credit.
If something looks wrong, include the URL and the inputs you used when you contact us. We correct factual mistakes and update the “last updated” stamp. We do not broker loans, pull credit, or negotiate with dealers on your behalf.
Limits of this calculator
Models are simplified on purpose so you can understand them. State tax on trade-ins, acquisition fees, documentary fees, lender overlay rules, balloon structures and commercial leases may need the lender’s own worksheet. Multi-state moves and business-use vehicles add more complexity.
Thanks for using a free tool responsibly. When you are ready, scroll back to the form, enter your numbers, and keep a copy of the output with your shopping notes.