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.
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.