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Auto Loan Calculator: Monthly Payment + Tax

Use this auto loan calculator to find your real monthly payment and total cost on any car loan. Includes down payment, trade-in value, and state vehicle sales tax in the math.

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Monthly payment$0
Loan amount$0
Total interest$0
Total cost of vehicle$0
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How this calculator works

Auto loan math has one wrinkle that other installment loans don't: most states tax (price − trade-in), not the full price, so a trade-in saves both the trade value AND the sales tax on that value. A few states (CA, HI, KY, MD, MI, MT, VA, DC) tax the full price.

loan = price + tax − down − trade
PMT = loan × r / (1 − (1+r)−n)

The 84-month loan is increasingly common but financially costly: longer term means more total interest AND a higher chance of being upside-down (owing more than the car is worth) for years. 60 months or less is the standard recommendation.

Source: Standard installment formula. State auto sales-tax rules — your state's Department of Motor Vehicles or Department of Revenue. Average U.S. auto loan rates — Federal Reserve G.19.

FAQ

How is a car loan calculated?
Three numbers determine your monthly payment: loan amount, APR (annual interest rate), and loan term in months. The formula is PMT = loan × r / (1 − (1+r)−n), where r is the monthly rate (APR ÷ 12) and n is the number of months. The calculator above runs this exact math, plus adds sales tax to the loan amount and subtracts your down payment and trade-in.
How much would a $30,000 car loan cost a month?
Depends on APR and term. At 7.5% APR over 60 months, a $30,000 loan runs about $601/month. At the same rate over 72 months, the payment drops to ~$518/month — but you pay nearly $1,800 more in total interest. Stretching the term lowers the payment but raises the cost.
What is a good APR on a car loan?
As of 2026, average new-car loan APRs are 6.5–8% for prime credit (FICO 720+), 8–10% for near-prime (660–719), and 11–17%+ for subprime. Used-car loans run 1–3 percentage points higher. Manufacturer 0% APR promo rates require top-tier credit and usually limit which models qualify.
How much should I put down on a car?
The traditional rule is 20% down on a new car or 10% on a used car. Putting more down reduces the loan amount, lowers the monthly payment, and avoids being 'underwater' (owing more than the car is worth) for the first 1–2 years. With 0% down, depreciation can put you upside-down in the first 6 months on a new car.
Should I take the dealer financing or shop my own loan?
Almost always shop your own first. Get a pre-approval from your bank or credit union BEFORE walking onto the lot — credit unions consistently beat dealer rates by 1–3 percentage points. Then if the dealer's manufacturer-promo offer (0% APR, etc.) beats your pre-approval, take that instead.
What's the 20/4/10 rule for buying a car?
Conservative car-buying guideline: 20% down minimum, 4-year (48-month) max term, and total transportation costs (loan + insurance + fuel + maintenance) under 10% of gross monthly income. It's strict — many people break it — but cars bought to this rule rarely cause financial stress.
Is it better to finance a new or used car?
Pure math favors used: a 2-3 year old car has already absorbed the steepest depreciation but typically has 80%+ of its useful life remaining. Used loans run 1-3 points higher APR than new, but the lower purchase price more than offsets the rate difference. Exception: if a manufacturer offers a 0% APR new-car promo and you qualify, that beats almost any used deal.
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