Plug in the dealer's numbers and see what you'll actually pay. Includes sales tax, doc fees, trade-in handling, and APR-vs-rebate analysis to detect dealer financing tricks.
Buying a car is one of the few transactions where the salesperson is actively trying to obscure the math. Monthly payment is the only number you'll be shown — not APR, not total paid, not the breakdown of fees vs. taxes vs. trade-in equity. This calculator lets you reverse-engineer the deal in your own spreadsheet, in private, before the dealer talks you into another four years of payments.
Inputs: out-the-door price (or break it down: MSRP + accessories + doc fees + sales tax + registration), down payment, trade-in value (vehicle worth + lien payoff if you owe more than it's worth), APR, and term in months. Output: monthly payment, total interest paid over the life of the loan, and the amortization schedule (how each payment splits between principal and interest).
The calculator also handles the "0% APR vs. $X cash back" decision dealers love to confuse. A 0% APR loan looks free, but you give up the cash incentive. Run the cash-back offer through a competitive bank financing rate (typically 6-8% in 2026) and compare the total cost. Often the cash-back wins by $2,000-$4,000 over the loan life.
Step 1 — Enter the out-the-door price. This is the total you sign for, including sales tax, doc fees, registration, and any add-ons (extended warranty, tire/wheel, paint protection, etc.). Don't enter MSRP — that's the sticker, not what you actually finance.
Step 2 — Subtract down payment and trade-in equity. If your trade-in is worth less than what you owe ('underwater'), the gap rolls into the new loan, which increases your principal. The calculator handles negative trade equity.
Step 3 — Enter APR and term. 60-month terms are typical. 72-month and 84-month terms are red flags — they exist mainly to make payments fit a budget on cars the buyer can't actually afford. The calculator shows the total interest for each term so the trade-off is explicit.
Enter the out-the-door price, down payment, APR, and term. The calculator returns your monthly payment, total interest paid, and a check on whether the dealer's '0% APR or $X cash back' offer is worth it.
Open the calculator →Run the math. The cash-back offer is real money off the principal. The 0% APR saves you interest at the cash-back loan rate. Example: $40k car, $3,000 cash back vs. 0% APR over 60 months. Cash back: finance $37k at (say) 7% APR, total interest ~$6,950, total paid $43,950. 0% APR: finance $40k at 0%, total paid $40,000. The 0% APR wins by $3,950 here. But at smaller cash-back amounts ($1,500 vs 0% APR), the math often flips toward cash-back.
Three reasons. (1) You pay much more total interest — for a $35k loan at 7%, 84 months costs ~$10,500 in interest vs ~$6,500 for 60 months. (2) You're underwater longer — depreciation outpaces principal paydown for 4+ years. (3) The monthly-payment view hides the affordability problem — if you can only fit the payment with an 84-month term, the car is too expensive for your budget. Stick to 60 months max; 48 if you can swing it.
Lease wins if: (a) you want a new car every 3 years, (b) you drive under the mileage cap (typically 12k/yr), (c) you use it for business (write-off advantage). Finance wins if: (a) you'll keep the car 5+ years, (b) you drive a lot, (c) you want zero monthly payments after the loan is paid off. Total cost over 9 years is almost always lower with finance-and-hold than with three sequential 3-year leases.
The 20/4/10 rule: at least 20% down, no longer than 4-year loan, and total transportation cost (loan + insurance + fuel + maintenance) under 10% of gross monthly income. By this rule, a $5k/mo household can afford about $30k total in cars. Looser rules accept 36 months loan and 15% transportation cost. The stricter the rule you follow, the less house-poor / car-poor you'll feel.