The sticker price is the least honest number at a car dealership. A $35,000 sedan financed at 7 percent for 60 months with $5,000 down and a $3,000 trade-in does not cost $35,000 — it costs about $40,078 once interest does its work, or roughly $535 leaving your bank account every month for five years. Stretch that same loan to 72 months and the payment drops to around $471, which feels like relief until you notice total interest climbing past $6,900. That tension — lower payment now versus more interest later — is the entire game of auto financing, and this calculator lays it bare before you sign anything.

Here is the math, step by step, with real numbers. Start with the amount financed: $35,000 minus the $5,000 down payment minus the $3,000 trade-in leaves $27,000 borrowed. Auto loans amortize monthly, exactly like mortgages, just on a shorter fuse. The monthly rate is 0.07 divided by 12 (about 0.583 percent), applied over 60 payments. The standard amortization formula — loan amount times the monthly rate times one-plus-rate to the 60th power, divided by that same power minus one — produces a fixed payment of $534.63. In month one, about $157.50 of that is interest and $377.13 reduces principal; by the final year the interest slice has shriveled to a few dollars. Total interest over five years: roughly $5,078. Add back your $8,000 of down payment plus trade-in and the true cost of the car is $40,078.

Dealers love to talk monthly payment instead of total cost for a reason: it hides the term trap. Extending from 60 to 72 months at the same 7 percent rate cuts the payment to about $471 — $64 less a month — but total interest jumps to roughly $6,900, an extra $1,800 for the privilege of paying longer. At 84 months, a term dealers now push routinely, you would pay over $8,600 in interest and spend the loan's middle years underwater, owing more than the car is worth as depreciation outruns your principal paydown. The rule of thumb used by every financially sane car buyer in America: keep the term at 60 months or less, and never finance for longer than you plan to keep the car.

Your trade-in and down payment are the two levers that matter most, because every dollar not borrowed is a dollar that never accrues interest. That $8,000 combined in our example saves about $1,504 in interest versus financing the full $35,000 at the same rate and term — and it shrinks the payment by roughly $159 a month. This is also why gap insurance exists: if you put little down on a car that depreciates 20 percent the moment you drive off the lot, you are immediately underwater, and gap coverage pays the difference if the car is totaled. With 20 percent or more down, you can usually skip it.

Interest rates on auto loans are brutally tiered by credit score, more so than most buyers expect. In the current US market, a borrower with excellent credit (780+) might land near 5.5 to 6 percent on a new car, while a subprime borrower under 620 can be quoted 12 to 18 percent — or worse at buy-here-pay-here lots. On our $27,000 loan, the difference between 6 percent and 14 percent is $518 versus $630 a month, and a staggering $4,100 versus $10,800 in total interest. Before you ever walk into a dealership, get pre-approved by your bank or a credit union; credit unions consistently beat dealer-arranged financing by a point or two, and walking in with a check in hand turns you from a payment buyer into a price buyer.

A few more US-specific realities to fold into your planning. Sales tax on the purchase — 6 to 10 percent depending on your state, though many states credit your trade-in against the taxable amount — is usually rolled into the loan or paid at signing; either way it is real money. Title, registration, and dealer doc fees add several hundred more. And the out-the-door price you negotiate should always be the focus, not the monthly payment: agree on the car's price first, then discuss financing as a separate transaction. The classic dealer four-square worksheet is engineered to blur these together — keep them apart and you keep the power.

Run the numbers for a used car too, because the math shifts. A $22,000 used SUV at 9.5 percent for 72 months with $2,000 down finances $20,000 at about $365 a month, with total interest near $6,300. Used rates run higher because the collateral is older, but the slower depreciation means you are less likely to go underwater. Either way, the calculator's total-cost figure is the number to compare across scenarios — it is the only one that tells the truth.

Leasing versus buying is the question every American car shopper eventually faces, and the math is less mysterious than dealers make it sound. A lease is essentially paying for depreciation plus interest over 24 to 36 months: on that same $35,000 sedan, a lease might cost $450 a month with $3,000 due at signing, versus $535 to own over 60 months. The lease looks cheaper monthly, but after three years you own nothing and face mileage penalties (typically 25 cents per excess mile over 10,000 to 12,000 a year), wear-and-tear charges, and the need to lease again. Buying wins for anyone who keeps cars past the loan term — years six through ten of ownership, with no payment at all, are where the real savings live. Lease only if you genuinely want a new car every three years and drive predictable, modest miles.

Certified pre-owned (CPO) is the sweet spot many buyers overlook. A 2- to 3-year-old CPO vehicle has already absorbed the steepest depreciation — roughly 30 to 40 percent off sticker — yet carries a manufacturer-backed warranty that rivals new-car coverage. Finance a $24,000 CPO sedan at 8 percent for 60 months with $4,000 down and you are financing $20,000 at about $406 a month, with total interest near $4,300. Compare that to $40,078 all-in for the new version of essentially the same car. The catch: CPO inventory is thinner and the best examples sell fast, so patience pays.

Refinancing an auto loan is one of the most underused money moves in America. If your credit score has climbed since you bought — say from 640 to 720 — or rates have fallen, refinancing that $27,000 balance from 9 percent to 6 percent with 48 months remaining drops the payment from about $672 to $634 and saves roughly $1,800 in remaining interest. Credit unions and online lenders like LightStream or PenFed will refinance with minimal fees, often under $100. The one trap: do not extend the term when you refinance just to chase a lower payment, or you will pay more interest overall while driving an older car.

Extended warranties and add-ons are where dealership finance offices make their fattest margins, so treat every offer with skepticism. A $2,500 extended warranty rolled into your loan at 7 percent actually costs about $2,950 with interest — and manufacturer CPO warranties or a reputable third-party plan bought independently often cost half as much. Paint protection, VIN etching, and nitrogen-filled tires are nearly pure profit for the dealer; decline them all. The only add-on worth considering is gap insurance, and even that you should price through your own auto insurer (often $20 to $40 a year) rather than the dealer's $500 to $800 package.

Before you touch the rate or term inputs, answer the bigger question: how much car can you actually afford? American personal-finance experts converge on the 20/4/10 rule — put at least 20 percent down, finance for no more than 4 years (48 months), and keep total car expenses under 10 percent of your gross income. On a $60,000 salary, that means roughly $500 a month all-in for the payment, insurance, and fuel. A $35,000 car with 20 percent down ($7,000) financed over 48 months at 7 percent costs about $649 a month — already over budget before insurance. The 20/4/10 rule would steer that buyer toward a $25,000 car instead: $5,000 down, $20,000 financed over 48 months at 7 percent is about $479 a month, leaving room for insurance. It feels restrictive because it is — that is the point. Cars are depreciating assets, and the rule keeps them from eating your wealth.

The monthly payment is only the headline of car ownership. Insurance on a financed vehicle runs $150 to $250 a month for full coverage — required by every lender, since the car is their collateral — and new drivers or expensive models pay more. Fuel, maintenance, and repairs add another $150 to $300. That $535 payment on our example sedan is really $850 to $1,000 a month all-in. AAA's annual driving-cost studies consistently put true ownership costs 60 to 80 percent above the loan payment alone. Budget the whole number, not the payment.

Zero-percent APR offers deserve special scrutiny because they are never free. Dealer 0% financing typically requires excellent credit, short terms (36 to 48 months), and — the real catch — forfeiting the cash rebate you would otherwise get. A $35,000 car with a $3,000 rebate financed at 5 percent for 60 months costs about $37,900 all-in; the same car at 0% for 60 months with no rebate costs $35,000, so the 0% deal wins there. But if the rebate is $5,000 and the alternative is 4 percent, the rebate-plus-loan can win. Always run both scenarios — the calculator's total-cost figure settles it in seconds.

The most expensive trap in auto lending is rolling negative equity into a new loan. Owing $18,000 on a car worth $14,000 and trading it in means the $4,000 shortfall gets added to your new loan — you start the next car already $4,000 underwater, paying interest on debt for a car you no longer own. Dealers love this rollover because it keeps you buying; your balance sheet hates it. If you are underwater, the cheapest move is usually to keep driving the car until the loan balance catches up with its value, making extra principal payments to get there faster.

Timing your purchase matters more than most buyers realize. Dealers operate on monthly and quarterly quotas, and the last few days of the month — especially quarter-end in March, June, September, and December — are when sales managers approve deals they would reject on the 5th. Model-year changeovers in late summer and fall bring manufacturer incentives on outgoing inventory. A $35,000 car bought at quarter-end with a $2,500 incentive instead of mid-month at sticker is $2,500 you never finance — worth about $50 a month and $3,000 in total cost over a 60-month loan.

New versus used is the eternal debate, and the depreciation curve settles it for most budgets. New cars lose roughly 20 percent of their value in the first year and about 15 percent per year for the next few — a $35,000 sedan is worth around $22,000 after three years. Buying that same car at three years old for $22,000 means someone else absorbed $13,000 of depreciation. Finance it at 8.5 percent for 48 months with $4,000 down and you are borrowing $18,000 at about $444 a month, with total interest near $3,300 — versus $40,078 all-in for new. The used buyer saves roughly $15,000 for driving a three-year-old car. Reliability data from sources like Consumer Reports can steer you to models that age gracefully; Toyota, Honda, and Mazda routinely top those charts.

A final word on where to borrow. Dealer-arranged financing is convenient and occasionally subsidized, but the finance office marks up the lender's buy rate — the difference between the rate the bank approved and the rate you are quoted is dealer profit. A pre-approval from your bank or credit union, secured before you shop, removes that markup entirely and turns the dealership negotiation into a pure price discussion. Online lenders have made this a 15-minute process; there is no reason to let the dealer be your only option.

With the pre-filled defaults — Vehicle Price $35,000, Down Payment $5,000, Trade-In Value $3,000, Interest Rate (APR) 7%, Loan Term 60 mo — the Auto Loan Calculator returns Amount Financed $27,000.00, Monthly Payment $534.63, Total Interest Paid $5,077.94, Total Vehicle Cost $40,077.94. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.