Enter your income, debts, and down payment to see your maximum home price, monthly payment, and whether you'll qualify for a mortgage.
Lenders use the "28/36 rule" to evaluate affordability. Your housing costs (PITI — principal, interest, taxes, insurance) should not exceed 28% of gross monthly income. Total debt, including housing, should not exceed 36%.
More lenient FHA loans allow up to 43% total DTI. Some conventional loans allow up to 50% DTI with strong compensating factors like high credit scores or large reserves.
Beyond your mortgage, budget 1–2% of home value annually for maintenance and repairs. A $400K home requires $4,000–$8,000/year on average for upkeep.
Property taxes vary widely — from 0.3% in Hawaii to 2.5%+ in New Jersey. HOA fees in condos or communities can add $200–$800/month. Factor all of these into your true monthly cost.
Credit score has an enormous impact on mortgage rates. The difference between a 620 and a 760 score can be 1–1.5% in interest rate — on a $400K mortgage, that's $80,000–$120,000 over 30 years.
Boost your score before applying: pay down revolving credit below 30%, dispute any errors on your credit report, and avoid hard inquiries for 6+ months.
Many states offer down payment assistance programs for first-time buyers, often providing grants or 0% interest second mortgages of $5,000–$25,000 toward your down payment.
FHA loans require only 3.5% down with a 580+ credit score. VA loans (veterans) and USDA loans (rural areas) require zero down payment. Check HUD.gov for state-specific programs.
This page aggregates published financial mathematics and figures from the primary sources below. Formulas and assumptions are set out on our methodology page, which also carries our corrections policy.
Mortgage underwriting starts from two ratios. The front-end ratio says housing costs (payment, taxes, insurance) should stay under 28% of gross monthly income; the back-end ratio says all debt payments together should stay under 36%. This calculator applies both and shows which one actually limits you — usually the back-end ratio, once car loans and student debt enter the picture.
Gross monthly income is $8,333. The 28% cap allows $2,333 for housing; the 36% cap allows $3,000 for all debts. With a $450 car payment and $300 in student loans ($750 total), the back-end test leaves $3,000 − $750 = $2,250 for housing — slightly tighter than the 28% test. Reserve roughly $430 of that for taxes and insurance and about $1,820–$1,900 remains for principal and interest, which at 6.5% over 30 years supports a loan of roughly $290,000–$300,000. Add your down payment to get the purchase price.
The ratios use gross income, but you spend net income — childcare, health premiums, and retirement contributions never appear in the formula. Maintenance (commonly estimated near 1% of home value per year), HOA dues, and PMI on low-down-payment loans all land on top. Many financially comfortable buyers deliberately stay two or three points under the caps; qualifying for a payment and living easily with it are different standards.
Affordability is exquisitely rate-sensitive: the same $1,900 monthly budget supports about $300,000 of loan at 6.5%, noticeably less near 8%, and more when rates fall. This is why buyers re-run affordability whenever rates move a half point, and why our salary-specific guides (see the $80k and $100k articles) show ranges rather than single numbers.
Is the 28/36 rule an actual lending requirement?
It is a widely used underwriting guideline rather than a law. Some programs allow higher ratios with strong credit or reserves — FHA loans in particular — but 28/36 remains the conservative planning benchmark.
Does the down payment change the ratios?
Indirectly and powerfully: a larger down payment shrinks the loan, the monthly payment, and often removes PMI, all of which relax both ratios for the same purchase price.
Should I include a partner's income?
Lenders count all borrowers on the application, including their debts. Run the calculator both ways — combined and single-income — to see how dependent the purchase is on both paychecks continuing.
Last updated: August 8, 2026 · Reviewed by the DollarDrill editorial team. Formulas follow standard published methods; see our editorial standards & sources. Results are educational estimates, not financial advice.