Auto Loan Calculator: Payment, Trade-In and Tax

What this calculator can help you understand

Your monthly payment, after your down payment, trade-in, sales tax and fees.
How much you’d finance, including any negative equity from a trade-in.
The total interest and total cost of the car, including your down payment.
How the loan term changes the payment and the interest.

When it’s useful

Before visiting a dealer, to know what payment a price really means.
When comparing loan offers, such as dealer financing versus a credit union.
When choosing a term, to see the trade-off between payment and interest.
When deciding whether to trade in, especially if you still owe on your current car.

Who it’s for

New and used car buyers financing a purchase.
People trading in a car they still owe money on.

What to enter

Input	What it means	Where to find it
Vehicle price	The negotiated price of the car	Your quote
Down payment	Cash you pay up front	Your budget
Trade-in value	What the dealer will credit for your current car	The dealer’s offer
Still owed on trade-in	The payoff amount on your current loan	Your lender’s payoff quote
Sales tax rate	Your combined state and local rate	Your state’s revenue department
Title, registration and dealer fees	Fees added to the purchase	The buyer’s order
Interest rate	The loan’s annual rate	Your lender or dealer
Loan term	How many months you’ll repay	Your loan choice
Tax after trade-in	Whether your state taxes the price after the trade-in value	Your state’s rules

How to use it

Enter the price, your down payment and any trade-in details.
Enter your sales tax rate and fees, and check the box if your state taxes the price after the trade-in.
Enter the interest rate and choose the term.
Read the monthly payment, then the amount financed and total interest.
Change the term to compare payments and interest.

Understanding your results

Amount financed = price + sales tax + fees − down payment − trade-in equity (trade-in value minus what you owe). If you owe more than the trade-in is worth, the difference is added.
Monthly payment is the fixed payment that repays that amount over the term.
Total interest is everything you’d pay beyond the amount financed.
Total cost is all monthly payments plus your down payment.

A worked example

Suppose you’ve negotiated a $32,000 car. You’ll put $3,000 down and trade in a car worth $8,000 that you still owe $5,000 on. Sales tax is 6% on the price after the trade-in, fees total $600, and you’re offered 7% for 60 months (a hypothetical rate).

Trade-in equity: $8,000 − $5,000 = $3,000.
Sales tax: 6% × ($32,000 − $8,000) = $1,440.
Amount financed: $32,000 + $1,440 + $600 − $3,000 − $3,000 = $28,040.
Monthly payment: $555.23 for 60 months.
Total interest: $5,274; total cost including your down payment: $36,314.

How the result changes

The same purchase with different terms:

Term	Monthly payment	Total interest
48 months	$671.45	$4,190
60 months	$555.23	$5,274
72 months	$478.05	$6,380
84 months	$423.20	$7,509

Stretching from 48 to 84 months lowers the payment by about a third but costs $7,509 in interest instead of $4,190.

Common mistakes

Negotiating the monthly payment instead of the price. A lower payment can hide a higher price or a longer loan.
Forgetting tax and fees. They can add thousands to what you finance.
Rolling negative equity into the new loan without noticing. It increases what you owe from day one.
Overlooking the cost of ownership. Insurance, fuel and maintenance come on top of the payment.

What to do with your result

Get a rate quote from your bank or credit union before you shop.
Ask the dealer for an itemized buyer’s order and compare it with your numbers.
If the payment stretches your budget, consider a lower price, a larger down payment or a shorter term.
Compare other loans with the loan calculator, or see how a car payment fits with other debts in the debt payoff calculator.

Limitations to keep in mind

The calculator assumes a fixed rate and equal monthly payments. Sales tax treatment, fees and rebates vary by state and dealer. It doesn’t include insurance, maintenance or depreciation. It’s an estimate, not a loan offer or financial advice.

Frequently asked questions

How long should a car loan be?

Shorter terms cost less interest but have higher payments. In our example, 48 months means $671.45 a month and $4,190 in interest, while 84 months lowers the payment to $423.20 but raises interest to $7,509. A longer loan also makes it more likely you’ll owe more than the car is worth for longer.

How does a trade-in affect sales tax?

In many states, sales tax applies only to the price after subtracting your trade-in’s value, which saves you money. Some states tax the full price. In our example, that’s the difference between $1,440 and $1,920 in tax. Check your state’s rules.

What is negative equity?

It’s when you owe more on your current car than it’s worth. Rolling it into a new loan increases the amount you finance. In our example, owing $11,000 on an $8,000 trade-in adds $3,000 and raises the payment to $674.03.

Should I compare the dealer’s financing with other lenders?

It often helps. Getting a rate quote from a bank or credit union before you shop gives you a point of comparison for the dealer’s offer.

What fees should I expect?

Common ones include title and registration fees set by your state and documentation fees charged by the dealer. Ask for an itemized buyer’s order showing every fee.

Does this include insurance and maintenance?

No. Insurance, fuel, maintenance and repairs are part of owning a car but aren’t part of the loan payment.

Auto loan calculator: see what a car will really cost each month and overall