From vehicle price to amount financed
The vehicle’s sticker price is only one part of the loan. This car payment calculator adds sales tax and fees, subtracts your down payment and trade-in value, and adds any remaining loan payoff on the vehicle you trade in.
A worked example you can check
A $30,000 car with $3,000 down, a $5,000 trade-in with no debt, $500 in fees and 6.25% tax on the full price finances $24,375.00. At 7% over 60 months, payment is $482.65, with $4,584.28 in interest.
Paying an extra $100 each month reduces interest by $934.35 and shortens repayment by 11 months, under the same assumptions.
Hypothetical inputs, not a current rate offer. Monthly interest and payments rounded to cents; final payment adjusted. Numerical fixtures checked with a separate Python Decimal implementation. See test cases.
How negative trade-in equity changes your loan
If your trade-in is worth $5,000 but its payoff balance is $7,000, you have $2,000 of negative equity. Rolling that difference into the next loan adds $2,000 to the financed balance before interest. Verify the actual payoff quote with your lender.
− down payment − trade-in value + trade-in payoff
Choose the sales tax assumption that fits the transaction
By default, tax applies to the full vehicle price. The alternative taxes max(vehicle price − trade-in value, 0). The old loan payoff never reduces the taxable price in this model. State and local rules vary, so verify how a trade credit, fees or rebates are treated. Enter additional non-taxable financed charges in the fees field.
What does “purchase cost” include?
Purchase cost before interest is vehicle price + modeled tax + entered fees. Purchase cost plus loan interest adds the calculated financing interest, which may include interest on rolled-in old debt. Down payment plus loan payments is the separate cash outflow figure; neither figure assigns an independent economic cost to your trade-in.
Will paying extra always save this much?
These savings assume declining-balance monthly interest, no penalty and immediate application of extra money to principal after monthly interest. Daily simple-interest loans or precomputed-interest contracts can behave differently. Confirm the contract’s payment rules.