What is this calculator for?
You're at a Toyota dealership looking at a $34,500 Camry. The salesperson punches numbers and says "we can get you in this car for $545 a month." You want to know if that's a good deal, what the interest rate works out to, what the total cost over the loan term will be. The auto loan calculator gives you the math behind whatever the F&I office is telling you — so you don't walk out paying $10,000 more than you should over the life of the loan.
Auto loan terms have been stretching dangerously. The average new car loan term in 2024 is 68 months (5.7 years) — up from 51 months a decade ago. Longer terms mean lower monthly payments but more total interest and a much higher risk of being "underwater" (owing more than the car is worth) for years. Auto rates as of 2024-25: 6-9% for new car loans for prime credit (700+ FICO), 9-15% for subprime, 4-6% for credit-union new-car promos.
This calculator computes monthly payment, total interest, total paid, and equity timeline (when do you stop being underwater on a financed car). Use it before signing — most car buyers should walk into the F&I office already knowing what monthly payment, rate, and term they'll accept.
How to use this calculator
Enter vehicle price (negotiated price, not MSRP), down payment, trade-in value (if applicable, less any remaining loan on trade-in), and any fees rolled into financing (sales tax, doc fees, extended warranty if you bought one).
The financed amount = vehicle price + rolled-in fees − down payment − trade-in equity. Many car buyers don't realize how much extra they're financing beyond the sticker price; the F&I office routinely adds 3-8% in "back-end" products (extended warranty, GAP insurance, paint protection, tire-and-wheel coverage) that get rolled into the loan.
Set the interest rate (APR). Get rate quotes from your bank or credit union BEFORE going to the dealer — the dealer's financing markup is typically 1-3 percentage points above what your bank would offer directly. Walking in with a pre-approved loan offer gives you negotiating leverage.
Choose the loan term: 36, 48, 60, 72, or 84 months. Shorter is better for total cost. Don't stretch to 84 months just because the salesperson offers it; the lower monthly is offset by 2-3× more interest and years of being underwater.
The calculator outputs monthly payment, total interest, total amount paid, and an equity timeline showing when your loan balance falls below the car's depreciated value.
Understanding your results
The calculator returns monthly payment, total interest, total amount paid, and a depreciation vs payoff curve showing when you reach positive equity.
How to read it. $34,500 car, $3,500 down + $2,000 trade = $5,500 down equivalent. Financed: $29,000 at 7% APR. 60-month term: monthly payment $574, total interest $5,440. 72-month: monthly $493, total interest $6,521. 84-month: monthly $440, total interest $7,960. The 84-month payment is $134/month cheaper than 60-month but costs an extra $2,520 in total interest. Plus you're underwater longer (the car depreciates faster than the loan pays down for the first 3-4 years of an 84-month loan).
The depreciation reality. Average new car loses 20-30% of value in the first year, 50-60% by year 5. A $34,500 car is worth ~$24,500 after year 1, ~$13,800 by year 5. If you financed $29,000 at 7% over 84 months, your loan balance after year 1 is still ~$26,000 — you owe more than the car is worth. This "underwater" period extends through year 3-4 on long-term loans. If you total the car in an accident: insurance pays only the depreciated value, you owe the remaining loan balance. GAP insurance covers this gap; many financed cars need it for the first 2-3 years.
The rate-comparison value. Same $29K loan, 60-month: at 5% APR (credit union typical) = $547/month, $3,830 interest. At 7% (dealer typical) = $574/month, $5,440 interest. At 11% (subprime) = $631/month, $8,860 interest. Same car, different lender = thousands of dollars different. Always get pre-approved at your credit union before negotiating; the dealer can match or beat to keep your business if their rate is worse.
The 20/4/10 rule. Personal finance guidance for healthy auto purchases: at least 20% down, no more than 4 year (48 month) term, all car-related expenses (loan + insurance + maintenance + gas) under 10% of gross monthly income. Adherence to this rule keeps people out of perpetual underwater car loans. Reality: most car buyers fail at least two of the three.
A worked example
Marcus, 32, needs a reliable car for his new commute. He's looking at: 2022 Toyota Camry SE certified pre-owned, $24,800. His credit score: 740 (good). Current car: 2014 Honda Civic worth $5,500 trade-in value.
Pre-shopping prep: Marcus gets pre-approved at his credit union for 5.49% APR on 60-month auto loan. Walks into the dealer with that approval in his pocket.
Dealer math: Camry $24,800 + tax (8%) $1,984 + doc fee $499 + title $75 = $27,358. Minus $5,500 trade. Financed amount: $21,858.
Dealer's F&I offer: 7.99% APR over 72 months = $381/month. Marcus says "my credit union pre-approved me at 5.49% over 60 months." F&I counter: 6.49% over 60 months = $427/month, total interest $3,756. Credit union: 5.49% over 60 months = $416/month, total interest $3,118. Credit union still wins by $638 over the loan.
Marcus also declines extended warranty ($1,800), GAP insurance from dealer ($600 — he can get GAP cheaper through credit union if he wants), paint protection ($400), VIN etching ($200). He accepted the basic financing only. The dealer makes less back-end money but Marcus saved $3,000 in declined add-ons plus the better rate.
Final outcome: $24,800 Camry, $5,500 trade, $21,858 financed at 5.49% over 60 months. Monthly $416. Total cost of ownership over 5 years (assuming $1,200/year insurance, $400/year maintenance, $1,800/year gas): about $44,000 all-in. Walking-out price was honest, financing was competitive, no rolled-in fluff.
Five years later: Marcus owns the Camry free and clear. Total interest paid: $3,118. Car worth roughly $14,000 (good condition trade-in). He keeps driving it another 5 years — by year 10 the car has cost him about $0.42/mile all-in, well below the $0.55-0.70/mile typical for new cars.
Related resources
For broader transportation cost analysis, see Fuel Cost Calculator and Gas Mileage Calculator. For tire and maintenance considerations, the Tire Size Calculator. For broader debt context including auto loans in DTI, the DTI Ratio Calculator. For the underlying loan math, the Loan Amortization Calculator. The CFPB's auto loan resource covers federal protections, common scams, and consumer rights in auto financing.