This car affordability calculator works backward from your budget to the highest vehicle price you can take on. It starts with a share of your gross income or a payment you choose, sets aside insurance, fuel and upkeep, and then counts your loan, cash, trade-in, sales tax and fees.
The guide below walks through every input and result, the budget bar, the 20/4/10 budget check and the mistakes that most often push a car budget too far.
Car Affordability Calculator
Set a budget from your income or from a payment you pick, add your cash and trade-in, then press Find My Price Limit.
Where the monthly car money goes
Estimates only. Starting values are examples, not offers. The loan is a fixed-rate loan with monthly payments, and tax and fees are treated as financed after your cash and trade-in equity. A lender also looks at your credit and other debts, so an approval can be higher or lower than this budget.
What Is a Car Affordability Calculator?
A car affordability calculator answers one question before you visit a dealer: how expensive a car can you buy without straining your budget? Most loan tools go the other way. You type in a price and they hand back a payment. This one starts with the money you have each month and turns it into a price ceiling.
The result is the most you can pay for the car itself, before sales tax and fees. That makes it a practical shopping number. You can filter listings by it, compare it with sticker prices and spot a car that is out of reach before you fall for it on a test drive.
Why Starting From Your Budget Matters
Shopping usually starts with a car and ends with a payment, and that order makes it easy to overspend. A dealer can reach almost any monthly figure by adding months to the loan, so a payment that “fits” can hide a price you cannot really carry.
Working backward puts the limit first. You decide what the whole car may cost you each month, take out the running costs, and only then size the loan. A car that is expensive to insure or fuel lowers the price you can afford, even when its sticker matches a cheaper-to-run rival. A budget built this way also leaves room for savings, housing and other goals, which is the point of a limit in the first place.
Inputs Used in the Calculator
Budget Source
Choose “A share of my gross income” to let the calculator set the monthly budget, or “A monthly loan payment I choose” if you already know the payment you want to stay under. Your income field stays visible in both modes, so the calculator can still compare total car costs with your pay.
Gross Annual Income
Household pay before taxes. The 20/4/10 guideline is stated with gross income. If you prefer to budget from take-home pay, use a lower share or switch to a fixed payment.
Budget Level and Share of Income
The dropdown fills the share field with 10%, 15% or 20%. The 10% level matches the 20/4/10 guideline. The 15% and 20% levels are simply looser budgets you can try to see what extra room costs you. You can type any share up to 50% and the dropdown switches to “Custom share”.
Running Costs
Insurance, fuel or charging, and a monthly set-aside for maintenance, repairs and parking. In income mode they come out of the budget before any money goes to the loan. A lender will require comprehensive and collision coverage on a financed car, so get an insurance quote for the models you are considering. For fuel, divide your monthly miles by the EPA rating at fueleconomy.gov and multiply by your fuel price.
Loan Term and APR
The term runs from 36 to 84 months. The APR is an example; enter the rate from a preapproval at a bank, credit union or online lender. Rates depend on credit, term, lender and whether the car is new or used, and they change over time, so the calculator does not assume one.
Cash Down, Trade-In and Amount Owed
Cash down and trade-in equity both reduce the loan. Equity is the trade-in value minus what you still owe on it. If you owe more than the car is worth, the gap is negative equity and is added to the new loan.
Sales Tax, Fees and the Trade-In Credit
Enter your combined state and local sales tax rate and an estimate of doc, title and registration fees. Leave the checkbox ticked if your state taxes only the price minus the trade-in. Most states do, but a few, California among them, tax the full price.
How the Calculator Works
The calculation runs in four steps.
- Monthly payment. In income mode: gross monthly income × share − running costs. In payment mode: the payment you entered.
- Loan size. The amount that payment repays at your APR and term: Loan = Payment × (1 − (1 + r) ^ −n) ÷ r, where r is the APR ÷ 1,200 and n is the number of months. At 0% the loan is the payment times the months.
- Money available. Loan + cash down + trade-in equity.
- Price. Take out fees and solve for the price that leaves exactly enough for sales tax: Price = (Loan + Down + Equity + Tax rate × Trade value − Fees) ÷ (1 + Tax rate). Without the trade-in tax credit, the “Tax rate × Trade value” part drops out.
Run the result forward and it balances: price plus tax plus fees, minus cash and equity, equals the loan.
What the Calculator Shows You
Highest Vehicle Price That Fits
The headline is the car’s price before tax and fees. Under it you see the payment, term and APR that produce it.
Monthly Loan Payment
The payment that fits your budget after running costs, or the one you chose.
Amount Financed and Total Interest
The loan that payment supports, and the interest you would pay over the full term. Total interest is a useful brake: a longer term raises the price limit, but the interest card grows faster.
Net Trade-In Equity
Trade-in value minus the amount owed. A minus sign means negative equity.
Cash and Equity Down
Your cash plus any positive equity, with its share of the price. This is the “20” in 20/4/10.
Car Costs vs. Gross Pay
The payment plus running costs as a percentage of gross monthly income. This is the “10”.
The Budget Bar and the Budget Check
The colored bar shows where the monthly car money goes: the loan payment in red, then insurance, fuel and upkeep. When the red part is small, running costs are eating most of the budget, and a car that is cheaper to insure or more efficient will raise your price limit more than haggling would.
The box under the cards tests your plan against the three parts of the 20/4/10 guideline: at least 20% down, a term of 48 months or less, and all car costs at or below 10% of gross monthly income.
- Comfortable fit: all three parts are met.
- Doable, with one stretch: one part is missed, and the box names it.
- Stretched thin: two or more parts are missed.
If you owe more on your trade-in than it is worth, a second box shows the negative equity. The guideline is a rule of thumb, not a lender requirement, and some versions count only the payment, or the payment and insurance, inside the 10%. The calculator uses the stricter version with all running costs included.
How to Use It Step by Step
- Pick the budget source: income or a fixed payment.
- Enter your gross annual income and choose a budget level, or type the payment.
- Add monthly insurance, fuel and upkeep for the kind of car you want.
- Choose a term and enter the APR from a preapproval.
- Enter your cash down, trade-in value and anything still owed on it.
- Set your sales tax rate, fees and the trade-in tax rule for your state.
- Press Find My Price Limit and read the price, cards and budget check.
- Change one input at a time, such as the term or down payment, to see what moves the limit.
An Example Budget
The starting values describe a household earning $90,000 a year that wants to keep all car costs at 10% of gross pay.
| Step | Result |
|---|---|
| 10% of $7,500 a month | $750 |
| Minus $375 running costs | $375 payment |
| Loan at 7%, 48 months | $15,660 |
| Plus $6,000 cash, $4,000 trade | $25,660 |
| Plus tax credit, minus $800 fees, ÷ 1.06 | $23,679 price |
Check it forward: $23,679 minus the $4,000 trade leaves $19,679 taxable, so tax is about $1,181. Price, tax and fees come to $25,660. Subtract $10,000 of cash and trade and $15,660 is financed. Interest over four years is $2,340, money down is 42% of the price, and the plan is a comfortable fit.
Move the budget level to 15% and the payment doubles to $750, because running costs stay the same. The limit jumps to $38,453, but the budget check drops to one stretch, since car costs now take 15% of gross pay.
Who Should Use It
First-Time Buyers
If you have never financed a car, the calculator shows how tax, fees and insurance shrink a budget that looks generous at first glance.
Buyers With a Trade-In
Enter the trade-in value and payoff to see how equity, or negative equity, changes your limit and the sales tax.
Families Comparing New and Used
Run the numbers twice. A used car may have a lower price but a higher APR and higher repair set-aside; a new car may cost more to insure. The better choice is the one whose total monthly cost fits.
Anyone Before a Dealer Visit
Knowing your ceiling before you talk numbers keeps the conversation on price, not on a payment that can be stretched.
Common Mistakes and Tips
- Treating take-home pay as gross pay. The 10% share is meant for gross income. With net pay, choose a lower share.
- Leaving out tax and fees. On a $25,000 car, 6% tax and $800 in fees add $2,300.
- Counting the trade-in twice. It lowers the loan once. It is not also an extra down payment.
- Stretching the term to reach a car. Each step from 48 to 84 months raises the limit, but you pay interest longer and can owe more than the car is worth for much of the loan.
- Draining the emergency fund. A larger down payment is good only if you still have cash for repairs.
- Ignoring other debts. Lenders compare all monthly debt payments with income, so a payment that fits on its own can be too much next to a student loan.
- Shopping right at the limit. Look for cars a little under the result. Final tax, fees and rate rarely match the first estimate, and a real dealer quote can be checked here before you sign.
Related Car Calculators
- Vehicle Loan Calculator
- Used Car Loan Calculator
- Out the Door Price Calculator
- Auto Refinance Calculator
- Early Car Loan Payoff Calculator
- Trade In Value Calculator
- Car Depreciation Calculator
- Auto Lease Calculator
Frequently Asked Questions
How much car can I afford on my salary?
Under the 20/4/10 guideline, all car costs should stay at or below 10% of gross monthly income. Enter your income and running costs and the calculator shows the highest price that fits after tax, fees and your down payment.
Is the 20/4/10 rule based on gross or take-home pay?
It is usually stated with gross pay, meaning income before taxes. If you budget from take-home pay, pick a lower share or switch to a monthly payment you choose.
Does the 10% include insurance and gas?
In the stricter version, yes: the payment, insurance, fuel and maintenance together. Some versions count only the payment. The calculator includes running costs, and you can set them to zero for the looser version.
Why does a longer loan raise the price I can afford?
The same payment repays more principal over more months. The trade-off is more interest and a longer stretch where you may owe more than the car is worth.
How does a trade-in change my price limit?
Positive equity works like cash down, and in most states it also lowers the sales tax. Negative equity is added to the new loan and lowers the price you can reach.
What APR should I use?
Use a real preapproval from a bank, credit union or online lender. Rates change over time and depend on your credit, so the starting value is only an example.
Will a lender approve me for this price?
Not necessarily. Lenders look at your credit history and total debt-to-income ratio. The calculator shows what fits your budget, which can be less than what a lender would approve.