Auto loan calculator
Most auto-loan calculators ignore that sales tax on the trade-in differs across states, gloss over dealer fees, and present 84-month financing as if it were a normal option. This one does all three honestly, and warns you when 84-month financing is going to cost you dramatically more total interest while leaving you underwater for years.
Last updated 2026-05-13
The vehicle
Sales tax
Financing
- Sticker price
- $35,000
- Sales tax (6.5%, net)
- +$2,275
- Fees
- +$500
- Down payment
- −$4,000
- Amount financed
- $33,775
- Total interest
- $6,832
- Total paid (loan)
- $40,607
- Total out of pocket
- $44,607
MethodologyHow sales tax + trade-in actually work
How sales tax + trade-in actually work
Tax net of trade-in (49 states + DC):sales tax is charged on (sticker − trade-in). Trading in a $10k car against a $35k purchase saves you tax on $10k — at a 6.5% rate that's $650 cash. Material to your math.
Tax on full sticker (CA, HI, KY, MI): tax is charged on the full sticker price regardless of trade-in. Selling the trade-in privately can sometimes net more cash, but takes time and effort. Worth modeling both ways.
Sales tax rates vary widely. No state sales tax: OR, MT, NH, DE, AK (state-level; local taxes still apply in AK). Combined state + local rates can exceed 10% in LA, TN, AR, AL. Check your DMV or recent vehicle-purchase paperwork for the exact figure.
Dealer feesinclude doc fees (which vary widely — some states cap them, most don't), title transfer, registration, and sometimes "delivery" or "preparation" fees. Typical total: $200-$1,200. These are usually rolled into the financed amount; we treat them that way here.
Why 84-month loans are a trap:on a typical $35k car at 7.5% APR, going from 60 to 84 months drops the monthly by ~$130 but increases total interest by ~50%. More importantly, the loan amortizes slower than the car depreciates — you'll owe more than the vehicle's worth (underwater) for years 1-5. If you trade or wreck the car during that window, you eat the gap.
0% promotional financingisn't free money. Dealers typically offer it instead of (not in addition to) a cash rebate. Run the math both ways — the rebate at 7.5% conventional financing often beats 0% over 60 months.