How Much House Can You Truly Afford? The 28/36 Rule, Explained With Your Numbers
Last updated: July 2026. Lenders don’t approve a mortgage based on what you’d like to spend — they use debt-to-income ratios that cap your housing payment and your total debt relative to income. Our free Home Affordability Calculator applies the same 28%/36% limits lenders typically use, so you get a realistic price ceiling before you start touring homes you can’t actually qualify for.
The two ratios lenders really apply
Most conventional lenders apply two limits simultaneously: your total housing payment (principal, interest, taxes, insurance, HOA) generally shouldn’t exceed about 28% of gross monthly income, and your total debt payments — housing plus car loans, student loans, credit cards — generally shouldn’t exceed about 36%. Whichever ratio is more restrictive for your situation sets your actual ceiling, which is exactly how automated mortgage underwriting tends to work in practice, regardless of which lender or loan program you ultimately apply through. Most affordability guesses skip the 36% check entirely and only think about the 28% housing number, which is why they’re often wrong for anyone carrying meaningful existing debt.
Why a $400 car payment can cost you $60,000 of home price
Because the back-end (36%) ratio caps your combined debt, every dollar of existing monthly debt directly reduces the mortgage payment — and therefore the home price — you can qualify for. On a $100,000 income, a $400/month car payment can reduce your affordable home price by tens of thousands of dollars compared to having no car payment at all, often by more than simply saving that same $400/month toward a bigger down payment would achieve. If your affordability number feels lower than expected, check which ratio the calculator flags as your binding constraint — existing debt is very often the real culprit, not the housing ratio itself.
Paying off debt vs. saving a bigger down payment
Because existing debt caps your ratio directly, paying off a car loan or credit card balance before applying for a mortgage frequently raises your max home price by more than putting that same money toward a larger down payment would. A bigger down payment lowers your loan amount, but a paid-off debt raises the entire ceiling the ratio allows — a distinction most affordability guides skip entirely. If you’re deciding between the two moves with limited cash, run both scenarios through the calculator and compare. As a rough rule of thumb, $10,000 applied to eliminating a $300/month debt tends to move the qualifying home price by more than $10,000 applied straight to the down payment, since paying off the debt loosens the 36% ceiling for every year of the loan going forward, not just the initial loan amount.
A worked example: two households, same income, very different ceilings
Consider two households, each earning $110,000 a year and each putting 10% down. Household A has no existing debt at all. Household B carries a $500/month student loan payment and a $350/month car payment — $850 a month combined. Household A’s affordable home price is set almost entirely by the 28% front-end ratio, landing somewhere around $430,000 at typical current mortgage rates. Household B, by contrast, hits the 36% back-end ceiling well before the front-end ratio becomes binding: their $850 in existing debt eats directly into the room left for a housing payment, pulling their affordable price down to roughly $340,000 — nearly $90,000 lower on identical income, purely because of the debt sitting in the back-end calculation. This is the scenario the calculator is built to surface, because a simple “28% of income” rule of thumb would tell both households the exact same number, which is simply wrong for Household B. It’s also why two households with identical gross income can walk into the same lender’s office and walk out with pre-approval letters nearly $100,000 apart — a gap that has nothing to do with credit score or interest rate and everything to do with debt already sitting on their monthly statements.
The mistake people make with a large down payment gift
A common assumption is that a large down payment gift from family automatically fixes an affordability problem, since it reduces the loan amount needed. That’s true up to a point, but a bigger down payment only ever affects the loan-amount side of the equation — it does nothing to relax the 36% back-end ratio if the real constraint is existing debt rather than the size of the mortgage itself. A buyer with $900 a month in car and student loan payments who receives a $50,000 gift toward their down payment will see their qualifying price rise somewhat, but they’ll often hit the same back-end ceiling again at a slightly higher price point, because the ratio is calculated against gross income and total debt, not against how much cash was put down. Compare that to the same buyer using that $50,000 windfall to pay off both loans entirely instead: the $900/month of debt disappears from the back-end ratio completely, freeing up nearly that entire amount toward a qualifying housing payment, which in most markets raises the ceiling by a considerably larger margin than the same dollars applied to a down payment ever could. Running the debt-payoff scenario and the down-payment-gift scenario separately through the calculator usually reveals which lever moves the ceiling further for a specific household.
What this calculator doesn’t include
The 28%/36% ratios are common industry guidelines, not universal rules — actual approved DTI limits vary by lender, loan program, credit score, and compensating factors, and some borrowers qualify above 36% back-end under certain loan types. This tool also doesn’t factor in Private Mortgage Insurance (PMI), which typically applies below 20% down and would reduce your affordable price further, nor does it account for how a higher credit score can sometimes unlock a more favorable interest rate and, indirectly, a higher qualifying price. It also treats property tax and homeowners insurance as flat percentage estimates rather than the specific figures a given county and insurer would charge, which can shift the housing-payment side of the ratio meaningfully in high-tax states or flood-prone areas where insurance premiums run well above the national average. Use it as a starting estimate before getting pre-approved, not a guarantee of what any specific lender will offer you once your full application and documentation are reviewed.
Find your real number
Head to the Home Affordability Calculator and enter your income, existing debts, and down payment to see your actual price ceiling and which ratio is limiting it. Once you have a number in mind, our Rent vs. Buy Calculator can help you decide whether buying at that price genuinely beats renting for your expected timeline, and our Debt Payoff Calculator can help you see how quickly clearing that car loan or credit card balance might raise your ceiling in the first place, and by roughly how much, before you commit cash to one strategy over the other.
Disclaimer: Freedom Wealth Lab provides general financial education, not personalized advice. Please read our full Disclaimer and Affiliate Disclosure before acting on anything you read here. The 28%/36% DTI ratios reflect standard U.S. mortgage-lending convention, not one regulator’s official rule.
