Car Affordability Calculator – How Much Car Can I Afford?

Most car shopping starts with a price, but a better place to start is the monthly payment you can comfortably afford. This calculator works backwards from that payment. It takes out the interest, sales tax and fees, adds your down payment and trade-in, and shows the most car you can buy. Then it checks the payment against your income, so you know whether the budget itself is sensible.

How to use the car affordability calculator

Enter the monthly payment you can afford.
Optionally enter your gross monthly income to check the payment against the 10% guideline.
Enter your down payment and trade-in value, minus anything you still owe on the trade-in.
Enter the interest rate, loan term, sales tax rate and fees.

The results show the car price you can afford, the loan amount, the total interest and the payment as a share of your income.

How the affordable price is calculated

First, the calculator finds how much you can borrow with your payment, using the present value of the payments:

loan = payment × (1 − (1 + r)^−n) ÷ r,   r = APR ÷ 12

Then it works out the price that leads to exactly that loan, after sales tax on the price minus the trade-in, fees, the down payment and the trade-in:

loan = price + tax × (price − trade-in) + fees − down payment − trade-in
price = (loan + down + trade-in − fees + tax × trade-in) ÷ (1 + tax)

Worked example

You can afford $500 a month and earn $6,000 a month before tax. You have $3,000 for a down payment and a $5,000 trade-in, and you expect 7% APR for 60 months, with 7% sales tax and $800 of fees.

$500 a month for 60 months at 7% repays a loan of $25,251.00.
The price that gives that loan is $30,655.14. Check: sales tax on $25,655.14 is $1,795.86, and 30,655.14 + 1,795.86 + 800 − 3,000 − 5,000 = $25,251.00.
You will pay $4,749.00 in interest over the loan.
The payment is 8.3% of your income, within the 10% guideline.

Tips for setting a realistic car budget

Budget the total cost of ownership. Insurance, fuel, maintenance and registration can add 50% or more on top of the payment.
Shop for the loan before the car. A pre-approval tells you your real APR, and a lower rate raises the price you can afford.
Negotiate the price, not the payment. Dealers can hit any payment by stretching the term. Use the car loan calculator to check the payment on the price you agree.
Keep the term short. Four or five years keeps interest low and helps you avoid negative equity.

Common mistakes

Forgetting tax and fees. They add thousands to the amount financed.
Using the trade-in’s value without subtracting what you owe. Negative equity reduces, not raises, what you can afford.
Using a rate you haven’t been offered. Your credit score affects the APR a lot. Check real offers first.
Maxing out the budget. Leave room for repairs and rising insurance costs.

Frequently asked questions

How much should I spend on a car?

A common guideline is the 20/4/10 rule. Put at least 20% down, borrow for no more than 4 years, and keep the car payment, insurance and fuel under 10% of your gross monthly income. Many people use 10–15% for the payment alone, but the lower your share, the more room you have to save.

Why is the car price lower than my budget times the number of months?

Part of every payment goes to interest, and sales tax and fees are added on top of the price. The calculator removes all of those, so the price it shows is what you can actually agree with the dealer.

Does a longer loan let me afford more car?

It lowers the payment, so you can borrow more, but you also pay more interest and are more likely to owe more than the car is worth for years. If you need 72 or 84 months to afford a car, it is usually a sign to choose a cheaper one.

Should I include insurance in my budget?

Yes. A newer or more expensive car usually costs more to insure. Get an insurance quote for the model you're considering and make sure the payment plus insurance, fuel and maintenance still fits.

Last updated October 31, 2026 · By the ZTool team