Auto Loan Calculator

How auto loan payments are calculated

An auto loan is a fixed-rate, fully amortizing installment loan: you borrow a lump sum — the amount financed — and repay it in equal monthly installments over a set term. Each payment is split between interest, charged on whatever balance remains, and principal, which reduces that balance. Early in the loan, more of each payment goes toward interest because the balance is largest; as the balance shrinks month after month, a growing share of each level payment goes toward principal instead. By the final scheduled payment, the balance reaches zero exactly.

From sticker price to amount financed

Before any interest math happens, this calculator works out how much you actually need to borrow. It starts from the taxable base — the vehicle price minus your trade-in value, since many states give you a tax credit for trading in a vehicle — taxableBase = max(0, price − tradeIn), then estimates sales tax as salesTax = taxableBase × (taxRate ÷ 100). The amount financed is the price minus your down payment and trade-in, plus that estimated tax:

loanAmount = max(0, price − downPayment − tradeIn + salesTax)

Note that not every state taxes on the net-of-trade-in basis — some tax the full purchase price regardless of trade-in. Sales tax rules vary by state and even by county, so treat the tax figure here as a planning estimate and confirm the exact method with your dealer or state department of motor vehicles.

The amortized-payment formula

Once the amount financed (P), monthly interest rate (r = APR ÷ 100 ÷ 12), and term in months (n) are known, the calculator solves for the level monthly payment (M) using the standard amortizing-loan formula:

M = P × [r(1 + r)ⁿ] / [(1 + r)ⁿ − 1]

When the rate is exactly zero — for example, a promotional 0% APR offer — that formula would divide by zero, so the calculator switches automatically to the simpler M = P / n. From the monthly payment, total of all payments is simply M × n, and total interest paid is (M × n) − P. The calculator also walks the schedule month by month internally — applying the interest charge on the remaining balance, then the rest of the payment to principal — to build the year-by-year amortization chart and table you see above.

Worked example — $32,000 vehicle, $4,000 down, $2,000 trade-in

Suppose you're financing a $32,000 vehicle, putting $4,000 down, trading in a vehicle worth $2,000, paying a 6% sales tax rate, over a 60-month term at a 6.5% APR. The taxable base is $32,000 − $2,000 = $30,000, so estimated sales tax is $30,000 × 6% = $1,800. The amount financed works out to $32,000 − $4,000 − $2,000 + $1,800 = $27,800.

With a monthly rate of r = 0.065 ÷ 12 ≈ 0.005417 and n = 60 months, the formula returns an estimated monthly payment of about $543.94. Over the full 60 months you'd pay roughly $32,636.34 in total — the $27,800 you financed plus about $4,836.34 of interest. By the end of year one the schedule shows roughly $4,863 of principal repaid against about $1,664 of interest, and that ratio flips steadily toward principal each year until the balance reaches zero at month 60. Try these exact numbers in the calculator above to see the full year-by-year breakdown, then adjust the term or APR to see how much each one moves your monthly payment and total interest.

Term length: monthly payment vs. total interest

The loan term is one of the biggest levers you control. Stretching the same amount financed over a longer term — say 72 months instead of 48 — divides the balance across more payments, which lowers each individual payment and can make a pricier vehicle feel affordable on a monthly basis. The catch is that the balance also takes longer to shrink, so it accrues interest for more months, which raises the total interest you pay over the life of the loan — sometimes by thousands of dollars compared with a shorter term at the same rate. A shorter term does the opposite: higher monthly payments, but a meaningfully lower total cost of borrowing. There's no universally "right" answer — it comes down to what fits your monthly budget versus how much you're willing to pay in total — but it's worth running both scenarios through the calculator before you commit.

What affects your APR

Lenders price auto loans based on a mix of factors: your credit score and credit history, the loan term, whether the vehicle is new or used (used vehicles often carry higher rates), the loan-to-value ratio, and prevailing market interest rates. Buyers with stronger credit profiles and shorter terms typically qualify for the lowest advertised rates, while longer terms, used vehicles, and thinner credit files tend to carry higher APRs. Comparing offers from your bank, a credit union, and dealer financing side by side is the most reliable way to find out what rate you genuinely qualify for — rather than relying on the advertised "as low as" number.

Beyond the loan payment

The monthly payment this calculator produces is only one slice of what owning a vehicle actually costs. A bigger down payment reduces the amount financed, which lowers your payment, cuts total interest, and helps you avoid being "underwater" — owing more than the car is worth — during the early months when depreciation is steepest. GAP insurance (Guaranteed Asset Protection) covers that gap between your loan balance and the car's actual value if it's totaled or stolen, and is worth considering if you put little down, financed for a long term, or rolled over negative equity from a previous vehicle. And beyond the loan itself, budget for total cost of ownership — auto insurance, fuel or charging, routine maintenance, registration and title fees, and depreciation — all of which continue well after the loan is paid off and can easily rival the loan payment itself over time.

Dealer financing vs. a bank or credit union

Dealer financing can be genuinely competitive — especially when manufacturers subsidize promotional rates — and it's convenient because it's arranged on the spot. A pre-approval from your bank or credit union, on the other hand, gives you a known rate to compare against and real negotiating leverage at the dealership, since you can simply walk away if the dealer can't beat it. Many buyers get the best of both worlds by securing a pre-approval first and then letting the dealer try to beat it.

Disclaimer

This calculator provides an estimate only and is not financial or lending advice. It models a simplified, fixed-rate, fully amortizing loan based purely on the figures you enter. Actual loan terms, fees (such as origination, documentation, and dealer add-ons), taxes, and the APR you're offered depend on your credit profile, your lender, your state, and the specific dealership — all of which can shift the real numbers meaningfully from what's shown here. Use this tool for ballpark comparison shopping, not as a financing offer, and always get a real, written quote from your lender or credit union before signing anything.