How Much Car Can You Afford?
By the TidyTally team · Last updated October 21, 2026
A car is usually the second-largest purchase most people make, and the monthly payment is only the start of the bill. Dealers often steer buyers toward a "what monthly payment works for you?" conversation, which can stretch the loan term and hide the real cost. This guide shows how to decide on a budget before you shop, and how loan terms change what you pay.
A starting rule: 20/4/10
A guideline popular with personal finance writers is the 20/4/10 rule: put at least 20% down, finance for no more than four years (48 months), and keep total transportation costs — loan payment, insurance, fuel and maintenance — under 10% of your gross income. It is a conservative benchmark, not a law, and many people find the 4-year loan hard in today's car prices. But it is a useful reality check.
What loan terms really cost
Consider financing $28,000 at 7.5%. The payment depends heavily on the term: about $677.01 a month for 48 months with $4,496 in interest; $561.06 for 60 months with $5,664 in interest; and $484.12 for 72 months with $6,857 in interest. Stretching from 48 to 72 months cuts the payment by about $193 but adds roughly $2,360 in interest. Try your own numbers in the Car Loan Calculator, which compares all the common terms at once.
The costs beyond the payment
Insurance, fuel or charging, maintenance and repairs, registration and taxes, parking and tires can add hundreds of dollars a month. Newer cars generally need less maintenance but cost more to insure and depreciate faster; older cars cost less to buy but can have unpredictable repairs. When comparing cars, estimate the total monthly cost of ownership, not just the loan payment.
Depreciation and being "underwater"
New cars typically lose a large share of their value in the first few years. If you finance most of the price with a long term and a small down payment, you can owe more than the car is worth — called negative equity or being "underwater." That becomes a problem if the car is totaled, or if you want to trade it in. A larger down payment, a shorter term and a vehicle that holds value reduce the risk. Gap insurance can help in the short term but is an extra cost.
New vs. used
Used cars, especially ones two to four years old, can offer substantial savings because the steepest depreciation has already happened. Certified pre-owned programs add warranty protection. New cars offer the latest features, warranties and sometimes promotional financing rates. Compare total costs, including interest — a promotional rate on a more expensive new car does not always beat a lower price on a used one.
How to shop smarter
Get pre-approved by a bank or credit union before visiting a dealer so you know the APR you qualify for, and use it as a benchmark against dealer financing. Your credit score strongly influences the rate. Negotiate the price of the vehicle first, then trade-in, then financing — separately. Be wary of add-ons rolled into the loan, since you pay interest on them too. Then check how the payment fits your plan in the Budget Calculator.
A simple budget method
Take your gross monthly income and multiply by 10% to set a ceiling for total car costs. Subtract estimated insurance, fuel and maintenance. What remains is the maximum for the loan payment. Then work backward with the calculator to find the vehicle price that fits, using a 48 to 60-month term. If the car you want is above that number, consider a larger down payment, a less expensive model or a certified used one.
Frequently asked questions
What is the 20/4/10 rule for buying a car?
It is a guideline to put at least 20% down, finance for no more than four years, and keep total transportation costs under 10% of your gross income.
Is a 72-month car loan a bad idea?
It lowers the monthly payment but increases total interest and the risk of owing more than the car is worth. Many financial educators recommend 60 months or less when possible.
How much should I put down on a car?
A common target is 20% of the price. More down means a smaller loan, less interest and lower risk of negative equity.
Should I finance through the dealer or my bank?
Compare both. Pre-approval from a bank or credit union gives you a benchmark rate; sometimes a dealer can beat it with promotional financing, but make sure the price is negotiated separately.