Compute your monthly car payment, total interest, and total cost. Includes sales tax and trade-in credit.
Monthly payment
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Loan amount
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Total interest
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Sales tax
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Total cost (vehicle + interest)
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Worked example
Picture a $35,000 car, a $5,000 cash down payment, no trade-in, a 7% sales tax, a 7.5% APR, and a 60 month term. Sales tax applies to the price after any trade-in, so it is 7% of $35,000, which is $2,450. The amount you actually finance is the price plus that tax minus the down payment, or $35,000 plus $2,450 minus $5,000, which is $32,450. Running $32,450 through the standard installment-loan formula at 7.5% over 60 months gives a monthly payment of about $650.23. Across all 60 payments you hand over about $39,013.89, so the interest portion is roughly $6,563.89. Adding the vehicle price and the sales tax to that interest, the all-in cost of owning the car comes to about $44,013.89. A bigger down payment or a shorter term both shrink the interest, while a longer term lowers the monthly payment but raises total interest.
| Item | Amount |
|---|---|
| Vehicle price | $35,000 |
| Sales tax (7%) | $2,450 |
| Down payment | -$5,000 |
| Amount financed | $32,450 |
| Monthly payment (7.5%, 60 mo) | $650.23 |
| Total interest | $6,563.89 |
| Total cost | $44,013.89 |
How it is calculated
The calculator first works out sales tax on the taxable price, which is the sticker price less any trade-in value, since most states tax only the net of a trade-in. It adds that tax to the price, then subtracts your down payment and trade-in to find the amount you finance. That balance is run through the fixed installment loan formula, which converts the annual percentage rate to a monthly rate and solves for a level payment that clears the loan over the chosen number of months. Total interest is simply the sum of all payments minus the amount financed. Total cost adds the vehicle price and sales tax to the interest so you see the true outlay, not just the monthly figure dealers like to quote. Note this is the loan cost only. It does not include registration, insurance, maintenance, or fuel, which together often rival the loan interest over the life of the car.