SmartCalc

This calculator is for informational purposes only and does not constitute financial advice. Results are estimates based on inputs you provide. Consult a qualified financial advisor before making financial decisions.

Auto Loan Calculator

Calculate your monthly car payment, see your amortization schedule, and factor in sales tax & trade-ins.

Vehicle Details

Trade-In Vehicle

Estimated Monthly Payment

$0

Total Financed (Principal)$0
Estimated Sales Tax$0

Total Interest Paid

$0

Total Cost of Loan

$0

Amortization Schedule

Dealership Negotiation Tip

Dealerships often try to negotiate based on the "Monthly Payment" rather than the actual price of the car. They can lower your monthly payment simply by stretching the loan term to 72 or 84 months, which costs you thousands more in interest. Always negotiate the Total Car Price and your Trade-In Value separately.

How to Calculate Your Car Payment

Buying a car is one of the largest financial decisions you will make. Our auto loan calculator helps you see past the dealership's monthly payment quotes and understand the absolute true cost of your vehicle. By inputting your vehicle price, down payment, trade-in value, and interest rate, you can generate an exact amortization schedule.

The Impact of Sales Tax and Trade-Ins

One of the biggest mistakes buyers make is forgetting to include sales tax and dealership fees in their calculations. In most states, trading in your vehicle gives you a massive tax break. For example, if your new car is $40,000 and your trade-in is worth $15,000, you only pay sales tax on the $25,000 difference. This calculator automatically applies this tax logic to estimate your total amount financed accurately.

If you run a dealership or calculate auto loan interest for clients, you may also find our margin calculator useful for determining your net profit on vehicle sales.

Frequently Asked Questions

How does my trade-in affect my car loan?

Your trade-in acts as a form of down payment. In most states, trading in a vehicle also provides a massive tax benefit. You only pay sales tax on the difference between the new car price and your trade-in value. For example, if you buy a $40,000 car and trade in a $15,000 car, you only pay sales tax on $25,000.

What happens if I owe more on my trade-in than it is worth (Negative Equity)?

Being 'upside down' on your current car loan means you have negative equity. If you trade it in, the dealership will simply take the remaining balance you owe and add it to your new car loan. This increases your total amount financed, your monthly payment, and the total interest you will pay.

What is a good auto loan interest rate?

Auto loan rates vary heavily based on your credit score and whether the car is new or used. Typically, new cars offer lower interest rates (often subsidized by the manufacturer, sometimes around 0% to 5%). Used car rates are higher, often ranging from 7% to 12% or more, depending on the age of the vehicle and your credit profile.

Should I take a 60-month or 72-month car loan?

A longer loan term (like 72 or 84 months) will automatically lower your monthly payment, making the car feel more affordable. However, you will pay significantly more in total interest over the life of the loan. Furthermore, cars depreciate rapidly—with a 72-month loan, you are at a much higher risk of having negative equity for a longer period of time.

Car dealerships excel at quoting monthly payments while obscuring what you're actually financing. Sales tax, title, registration, and dealer fees can quietly add thousands. Trade-in value reduces what you finance — and in many states, also reduces taxable amount. The real number you should care about is your fully-loaded monthly payment.

Auto loan amortization

Same as a mortgage: M = P × [r(1+r)^n] / [(1+r)^n − 1]. The variable to watch is P (financed amount), which equals (price − down payment − trade-in + sales tax + dealer fees). In about 40 US states, your trade-in reduces the taxable price as well — meaningful savings on a higher-priced car.

When to use this calculator

Run it before you walk into a dealer. Decide your max monthly payment based on income — the conservative rule is that all car expenses (payment, insurance, gas, maintenance) should be under 15% of take-home pay. Then back into the price you can afford. Avoid 72+ month loans: they keep monthly payments low but leave you upside-down (owing more than the car is worth) for years.

Worked example

A $35,000 vehicle with $5,000 down, an $8,000 trade-in, 7% sales tax, and a 60-month loan at 7%. Financed amount: $35,000 − $5,000 − $8,000 + tax. In a state where trade-in reduces taxable amount, the tax is 7% of ($35,000 − $8,000) = $1,890. Total financed: $23,890 → $473/month. Total paid: $28,393. Total interest: $4,503.