Mortgage Affordability Calculator: How Much House Can You Really Afford?

What this calculator does differently

You've probably seen mortgage calculators that ask for income and spit out some impressive number. Then you talk to a lender and the actual approval comes in way lower. That gap exists because most basic calculators only look at principal and interest.

Real lenders don't work that way. They add up your full monthly housing cost: the mortgage payment itself, property taxes, homeowners insurance, PMI if you're putting less than 20% down, and any HOA fees on top of that. All of it has to fit under their debt ratio limits.

Our affordability calculator does the same thing. It includes every one of those components, then works backward from your income to find the highest home price where everything still fits within the 28/36 guidelines. The result matches what lenders will actually approve, not some fantasy number.

How the 28/36 rule works in practice

Two ratios control how much mortgage you qualify for, and most people only know about one of them.

The front-end ratio (28%) caps your total housing costs at 28% of gross monthly income. If you earn $7,083 per month before taxes (that's an $85,000 salary), your max housing payment is $1,983. That includes everything: principal, interest, taxes, insurance, PMI, HOA.

The back-end ratio (36%) looks at all your debts combined. Housing costs plus car payments, student loans, credit card minimums. For that same $7,083 monthly income, the total debt cap is $2,550.

Here's where it gets interesting. If you're carrying $500 a month in other debt, the back-end ratio limits your housing payment to $2,050 ($2,550 minus $500). In this case the front-end ratio at $1,983 is actually the tighter constraint. The calculator picks whichever limit is lower. That's what trips people up. They look at one ratio and forget the other can be the one holding them back.

The number the bank gives you vs. the number you should use

Getting approved for $272,000 and comfortably affording $272,000 are two different conversations.

Banks evaluate your gross income. That's the number before federal taxes, state taxes, retirement contributions, and health insurance premiums disappear from your paycheck. On $85,000 gross, your actual take-home is more like $4,800 to $5,100 a month depending on your state and deductions. A $1,976 housing payment chews through roughly 39% to 41% of that.

That leaves $2,800 to $3,100 for groceries, transportation, utilities, childcare, subscriptions, savings, and everything else. Is that comfortable? Depends entirely on your life. Someone sharing expenses with a partner in a low-cost area might barely notice it. A single parent in a metro area with daycare costs would feel stretched thin.

A lot of financial planners suggest targeting 25% of take-home pay for housing. On $4,900 monthly take-home, that's about $1,225, which is well below the $1,976 the bank approved. The gap between those two numbers is where personal judgment lives. Check our amortization guide to see how different price points change where your money actually goes each month.

Five things that move your affordability number

Interest rates have an outsized effect

On a $300,000 loan, the difference between a 6% and 7% rate adds $197 to your monthly payment. Over 30 years, that one percentage point costs an extra $71,000 in interest. And it works in reverse for affordability: at 6%, the calculator approves you for $288,000. At 7%, that drops to $268,000. A single point swing moves your budget by about $20,000. There's a detailed breakdown of how this plays out in our 15 vs 30-year comparison.

Your down payment pulls double duty

Putting more down obviously reduces the loan balance. But crossing the 20% threshold eliminates PMI, and that matters more than most people realize. On a $232,000 loan at 0.5% PMI, you're paying $97 a month that builds zero equity. It's pure insurance for the lender. Get rid of that $97 and the calculator redirects it toward a bigger mortgage, adding real buying power to your budget.

Existing debts eat directly into your ceiling

A $400 car payment doesn't just cost $400. It reduces how much house you can qualify for by roughly $42,000. The back-end DTI ratio is why. Every dollar of monthly debt directly subtracts from the housing payment your lender will allow. I've seen people pay off a car loan right before applying for a mortgage and unlock a noticeably better home in a better neighborhood. Sometimes the math on that trade-off is obvious.

Property taxes vary more than you'd think

New Jersey's average effective property tax rate runs around 2.2%. Colorado sits closer to 0.5%. On a $300,000 home, that's the difference between $550 per month and $125 per month in property taxes alone. If you're comparing homes across state lines, or even between neighboring counties, the tax rate shifts your effective affordability as much as the interest rate does.

HOA fees are a permanent cost

A $350 monthly HOA fee hits your DTI the same way $350 in car payments would. Lenders treat them identically. That same $350 in HOA reduces your maximum home price by about $44,000 compared to a property with no HOA. A condo that looks cheaper on paper can actually be more expensive from a qualification standpoint once you factor in the dues.

How to use the calculator without fooling yourself

Open the mortgage affordability calculator and plug in your real numbers. Not aspirational ones. Your actual income, the debts you actually carry, the savings you actually have.

Then run three versions:

• Aggressive: Minimum down payment, current debts only. This is the ceiling. The absolute max a lender might approve.
• Realistic: Your planned down payment, current debts. This is where you should be shopping.
• Stress-tested: Add $200 to the monthly debts field to simulate unexpected costs. If you can still afford the house in this scenario, you've got a real cushion.

If only the aggressive number works, the house is too expensive. If the stress-tested number still feels fine, you're in good shape. Most people should land somewhere in between.

Once you've settled on a price range, run that loan amount through the mortgage overpayment calculator to see how even small extra payments from day one can build equity faster and save you thousands over the life of the loan.

Mistakes that quietly cost buyers money

The biggest one is forgetting closing costs exist. Plan for 2% to 5% of the purchase price. On a $272,000 home, that's $5,400 to $13,600 that comes out of pocket at closing, separate from your down payment. If your savings are exactly enough for the down payment and nothing more, you're going to hit a wall.

Maintenance is the other blind spot. The standard rule of thumb is 1% of the home's value per year for upkeep. For a $272,000 home, that's $2,720 annually, or about $227 per month you should be mentally budgeting even though nobody sends you a bill for it. New roof, busted water heater, HVAC repair. These things don't happen every month, but they do happen. Our overpayment guide helps you think through how to balance extra mortgage payments against keeping a healthy cash reserve for exactly these situations.

And don't forget: the rates you see advertised online typically assume excellent credit, a 740+ score. If you're at 680, your actual rate might be 0.5% higher. Based on the affordability math, that costs you around $10,000 in reduced buying power. Worth checking your score before you get too attached to any listing.