Monthly payment with tax, trade-in, and negative equity handled correctly — plus what each loan term really costs.
In most states tax applies to price minus trade-in. Anything still owed on the trade rolls into the new loan.
| Term | Payment | Total interest | Total paid |
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Longer terms buy a lower payment with more interest — and more months underwater on a depreciating asset.
This auto loan calculator turns price, down payment, trade-in, sales tax, and rate into a monthly payment, correctly rolling any negative equity from your old vehicle into the new loan. It also shows the total interest each term length adds.
The amount financed is the car's price plus sales tax, minus your down payment and trade-in value, plus any negative equity rolled in from a loan you still owe on the trade. That total is amortized over your term at the loan rate. Because tax is charged on the price (often net of trade-in) and negative equity adds to the balance, the financed amount can be larger than the sticker price.
We add sales tax to the price, subtract your down payment and trade-in value, add any negative equity, then amortize the result over your loan term at the given rate.
It means you owe more on your current car than it is worth. That gap gets added to the new loan, increasing the amount financed.
A longer term lowers the monthly payment but increases total interest paid. The calculator shows both so you can see the trade-off.
A longer term lowers the monthly payment but increases total interest and the time you spend underwater. The term-comparison table shows exactly how much each extra year of loan costs.
It means you owe more on your current car than it's worth. That gap is added to the new loan, so you finance the old shortfall on top of the new car — a common way buyers end up underwater again.
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