How to use this calculator
Estimate an auto-loan payment after accounting for a vehicle’s price, trade-in, down payment, sales tax and financed fees. This makes it easier to distinguish the purchase price from the amount actually financed.
From vehicle price to loan principal
This model applies sales tax to vehicle price minus trade-in value, with the taxable amount never falling below zero. It adds that tax and entered fees to the vehicle price, then subtracts trade-in value and down payment to obtain loan principal.
Monthly payments use a fixed nominal annual rate divided by 12. A zero-rate offer divides the financed principal equally across the selected number of months. The interest shown in the schedule is charged on each opening balance.
Understand the assumptions
The trade-in tax treatment is an explicit assumption, not a calculation of local tax law. Check whether a dealer’s quote taxes the full vehicle price or grants a trade-in credit. The model does not include an outstanding loan on the traded vehicle; negative equity needs separate consideration.
Extra payments reduce principal each month and can shorten repayment. The last payment is capped at the remaining balance plus that period’s interest. Fees are assumed financed, and the estimate excludes rebates, changing rates, lender-specific rounding and prepayment penalties.
Example: a zero-rate purchase
For a $30,000 car, a $5,000 trade-in, $3,000 down, 6% tax and $500 in fees, modeled tax is $1,500 and purchase cost is $32,000. The financed balance is $24,000. At 0% for 48 months, the payment is $500.