Monthly payment, interest and total cost for an auto loan with tax + fees.
Standard amortization on the financed amount = price + tax + fees − down payment − trade-in. Sales tax is applied on price minus trade-in (the typical US rule).
A car loan is the second-largest piece of consumer credit after a mortgage, and the one where buyers most consistently overpay. Dealers focus the negotiation on the monthly payment, which is the variable easiest to soft-pedal (just lengthen the term), while the total cost — price + tax + fees − trade-in + interest — quietly inflates by 30–60 % above the sticker price. A 28 000 € car at 6.5 % APR on a 60-month loan with 6 % sales tax and 200 € in fees costs roughly 35 200 € all-in. Stretch the term to 84 months and the monthly drops by 40 €, but the interest jumps from 4 600 € to 6 600 €. This calculator separates the variables — vehicle price, down payment, trade-in, APR, term, sales tax, fees — so the buyer can negotiate the right one (price, not payment).
Sales tax applies to the taxable base (price minus trade-in in most US states; price alone in most EU jurisdictions; the calc uses the trade-in deduction): tax = (price − trade-in) × tax_rate.
Amount financed = price + tax + upfront_fees − down_payment − trade-in.
Monthly payment = financed × r / (1 − (1 + r)^−n), where r = APR / 12 and n is the number of months. For r = 0, payment = financed / n.
Total paid = pmt × n. Total interest = total paid − financed. All-in cost = down_payment + trade_in (as your "spend") + total paid.
The cost-breakdown stack chart shows three components proportionally: principal financed, interest, sales tax. (Up-front fees fold into the principal silently because they're financed.)
Enter the vehicle price the dealer agreed to (after negotiation, not the sticker), the down payment you'll write a check for at signing, the trade-in value you've been quoted (carfax/edmunds online quotes are the realistic ceiling), the APR the lender quoted, and the term in months. Add sales tax (6 % is typical in many US states; in EU countries the price is usually inclusive, so set 0). Add the upfront fees (registration, document fee, dealer fee — typically 100–500 €). The calc returns the monthly payment as the headline KPI, plus the financed amount, total interest, sales tax, all-in cost, and a stacked-bar visualization.
New compact: price 28 000 €, down payment 4 000 €, no trade-in, APR 6.5 %, term 60 months, sales tax 6 %, upfront fees 200 €.
Stretch to 84 months at the same rate: monthly drops to 387 €, but interest jumps to 6 626 €.
Quoted APR vs effective APR. Lenders sometimes quote a "nominal" rate that excludes origination fees and the financing of those fees. The legal definition (US Reg Z, EU TAEG) requires those fees to roll into the APR. If you've separately listed the upfront fees as financed, don't double-count by also using the higher fee-inclusive APR.
Negative equity from a trade-in. If you owe more on your current car than it's worth, the negative equity gets added to the financed amount, not subtracted. Set "trade-in" to a negative number (or zero) and add the deficit to "upfront fees" to model this correctly.
Add-ons silently financed. Dealers love to add gap insurance, extended warranties, paint protection. Each adds 500–2 000 € that quietly enters the financed amount. The calc lets you set "upfront fees" — bundle the add-ons there to see the all-in payment.
Variable-rate auto loans. Rare but present (mostly subprime). The calc assumes fixed rate. If yours is variable, the payment recomputes when the index moves; treat the result as an entry-month estimate.
Sales tax on financed amount, not just price. A few jurisdictions tax the full price + the rolled-in fees (Texas, Maryland for some sales). The calc taxes (price − trade-in), which is the most common rule. Adjust manually if your state taxes the financed amount.
Lease vs loan. A lease is a different math entirely (depreciation share + money factor, not amortization). Don't compare a lease payment to a loan payment without total-cost-of-ownership math.
Out-the-door price illusion. The number the dealer quotes is sometimes "monthly payment" without context. Always negotiate the price, then derive the payment — never the other way around.
Down payment too small. Below 10 % down, you risk being "upside down" (owing more than the car is worth) for the first 12–18 months due to depreciation. Gap insurance is sold to cover this gap; if you put down 20 %+ you generally don't need it.