About the Auto Loan Calculator
An auto loan calculator estimates the monthly payment, total interest, and total cost of financing a new or used vehicle. Beyond the headline payment, the calculator helps you compare loan terms, evaluate dealer financing against credit-union or bank offers, and see how much a trade-in, down payment, or sales tax change the bottom line.
Why the sticker price isn't the price you finance
The amount you actually borrow is the out-the-door price plus tax and fees, minus your down payment and trade-in value. Sales tax in most U.S. states is calculated on the price after trade-in (a real benefit when trading in a paid-off car), but a handful of states tax the full price. Doc fees, title and registration, and dealer add-ons can add $500–$2,000 that quietly gets rolled into the loan.
Two cars at the same monthly payment can have very different total costs. A $30,000 car at 6% over 60 months and a $33,000 car at 9% over 72 months can both come in around $580/month — but the second costs roughly $5,000 more in interest and leaves you upside-down on the loan for far longer.
Term length and the underwater problem
U.S. auto loan terms have stretched from a typical 48 months a generation ago to 72- and 84-month loans being commonplace. Longer terms reduce monthly payments but make the loan more expensive in two ways: more total interest, and a much longer period of negative equity (owing more than the car is worth).
A new car typically loses 20–30% of its value in the first year. On a 72-month loan with 10% down, you can be $5,000–$8,000 underwater for two years or more — a real problem if you total the car or need to sell. Gap insurance addresses the totaling case but doesn't help if you simply outgrow the vehicle.
Dealer financing vs. pre-approval
Dealers earn a markup on the financing they arrange (the difference between the rate the lender approves you for and the rate offered to you, often 1–2 percentage points). Walking in with a pre-approval from a credit union or bank — typically the lowest auto-loan rates in the market — gives you a benchmark to negotiate against.
Sometimes the dealer can match or beat your pre-approval, especially with manufacturer-subsidized rates on new cars. The point of the pre-approval isn't to lock in a rate; it's to remove information asymmetry from the negotiation.
How it works
- Compute the financed amount. Vehicle price + sales tax + fees − down payment − trade-in value (minus any trade-in loan balance you're rolling in).
- Apply the amortization formula. The same formula used for mortgages: monthly rate, number of payments, and principal produce a fixed monthly payment.
- Compare against alternatives. Run the same numbers at a different term, with a larger down payment, or with the rate from a pre-approval. Small input changes can move total cost by thousands.
Formula
- M = Monthly payment
- P = Amount financed (price + tax + fees − down − trade)
- r = Monthly interest rate (APR ÷ 12)
- n = Number of monthly payments (term in months)
Worked examples
$32,000 car, $4,000 down, 7% APR, 60 months
Financed amount = $28,000. Monthly payment ≈ $554. Total paid ≈ $33,250, of which $5,250 is interest.
Same car, 72-month term
Financed amount = $28,000. Monthly payment ≈ $478 (saving $76/month) but total interest ≈ $6,400. You pay roughly $1,150 more for the longer term.
Dealer rate vs. credit-union pre-approval
$28,000 financed over 60 months: at 9% APR (typical dealer-arranged rate for a mid-credit borrower) the monthly payment is $581 and total interest $6,860; at 6% APR (typical credit-union rate) it's $541/month and $4,470 in interest — a $2,390 difference for the same car.
Frequently asked questions
What credit score do I need for a good auto loan rate?
Auto-loan rate tiers vary by lender, but the best rates generally go to scores above 720. Borrowers in the 660–719 range typically pay 1–3 points more; below 660, rates can be 5+ points higher. Improving a score from 680 to 740 before applying can save thousands over the life of the loan.
Should I take the dealer rebate or the low APR?
Manufacturers often offer a choice between a cash rebate and a subsidized APR. Run both numbers: the rebate reduces the loan amount up front, the low APR reduces interest over time. The break-even depends on the loan size and term, but rebates often win for shorter terms or large down payments.
Is it better to lease or buy?
Leases minimize the monthly payment for a given car but you build no equity. Buying with a 36–60 month loan and keeping the car well past the loan's end is usually the cheapest long-run option for someone who drives a typical 12,000–15,000 miles per year and keeps cars 8+ years.
Should I put more money down?
A larger down payment reduces interest paid and shortens the period of negative equity, but only down to about 20%. Beyond that, the marginal benefit shrinks. If your savings could earn more invested, a moderate down payment plus aggressive principal payments is often a better use of cash.
What is gap insurance?
Gap insurance covers the difference between your loan balance and the car's actual cash value if it's totaled or stolen. It's most useful in the first 1–3 years of a loan with a low down payment, when negative equity is largest. It's typically $20–$40/month from your auto insurer or a one-time $300–$700 from the dealer.
Can I refinance an auto loan?
Yes — and it often makes sense if your credit improved meaningfully since you took out the loan, or if you took dealer financing at a markup. Most refinances have minimal closing costs, so even a 1-point rate reduction can pay back quickly.
Related calculators
Concepts
Sources & methodology
- Consumer Financial Protection Bureau — Auto loan basics — source