How to use this calculator
- Enter the Vehicle price and your cash Down payment.
- Add your Trade-in value if you have one; this calculator taxes only the price after the trade-in.
- Fill in Sales tax, the Interest rate and the Loan term in months.
- Read the Monthly payment, Loan amount, Total interest and Total cost of the car.
How the car loan amount is built
The amount you finance is not the sticker price. Sales tax is added, then your down payment and trade-in are subtracted. In many US states the tax applies only to the difference between the price and the trade-in value, which is how this calculator works; check your state's rule, because some tax the full price.
Loan = Price + (Price − Trade-in) × Tax% − Down payment − Trade-in; M = Loan · r / (1 − (1 + r)^−n)- Price = vehicle price
- Tax% = sales tax rate as a decimal
- r = monthly interest rate (annual rate ÷ 12 ÷ 100)
- n = number of monthly payments
The monthly payment then comes from the standard installment formula.
Example: a $35,000 car over 60 months
Take a $35,000 vehicle with $5,000 down, 7% sales tax and a 7% rate over 60 months. Tax is $2,450, so you finance $32,450. The payment is $642.55 and the interest totals $6,103. Including the $5,000 down payment, the car costs $43,553 in all.
Notice that the car costs about $8,500 more than its price: $2,450 of tax plus $6,103 of interest.
Term length: the trap of the low payment
Stretching the loan makes the payment friendlier and the car dearer. On the same example, 48 months gives $777.06 a month and $4,849 interest; 60 months gives $642.55 and $6,103; 72 months gives $553.24 and $7,383.
A long loan has another danger: cars lose value quickly, so after a few years you can owe more than the car is worth. That makes it costly to sell or trade in early. A common guideline is to keep the term as short as your budget allows.
What a trade-in does
Add an $8,000 trade-in to the 60-month example and the taxable amount falls to $27,000, so tax drops to $1,890. The loan shrinks to $23,890, the payment to $473.05, and interest to $4,493. A trade-in helps twice: it lowers the balance and it can lower the tax.
Before you accept a dealer's figure, get a quote from a used-car buyer or an online appraisal so you know the car's real value. Compare financing offers with the general loan calculator and see what extra payments do in the loan payoff calculator.
Common mistakes
- Shopping by monthly payment alone; ask for the price, rate, term and total cost separately.
- Forgetting insurance, fuel, registration and maintenance, which are not part of the loan.
- Rolling negative equity from an old loan into the new one.
- Accepting dealer financing without a pre-approval from a bank or credit union to compare.
- Adding add-ons such as extended warranties into the loan without pricing them separately.
Assumptions and limits
The calculator assumes one sales-tax rate, a fixed interest rate and equal monthly payments. It does not include title and registration fees, documentation fees, rebates, dealer add-ons, gap insurance, or tax rules that differ by state. Leases are a different product and are not covered.
Treat the result as an estimate and compare it with the dealer's or lender's written offer.
Frequently asked questions
How much car can I afford?
Work backwards from a monthly payment you can pay comfortably, then add insurance and running costs. Try several prices and terms here until the payment fits.
Is sales tax financed in a car loan?
Often yes. The calculator adds the tax to the amount financed, which is why the loan can be larger than the price minus your down payment.
Is a 72-month car loan a bad idea?
It lowers the payment but raises total interest and raises the chance of owing more than the car is worth. A shorter term is cheaper if you can afford the payment.
Does a bigger down payment help?
Yes. It reduces the amount financed, the interest, and the risk of negative equity.
Does a trade-in reduce sales tax?
In many states it does, because tax is charged on the price minus the trade-in. Rules vary, so confirm with your state's revenue department or dealer.