The 28/36 guideline
Lenders look at two debt-to-income (DTI) ratios, each measured against gross monthly income:
- Housing ratio: the full house payment (principal, interest, taxes, insurance, PMI). A classic limit is 28%.
- Total debt ratio: housing plus car, student loan and credit card payments. A classic limit is 36%, though many programs allow 43% to 50% with strong credit or reserves.
The calculator uses whichever limit is tighter, then finds the highest price whose full payment fits.
Example
With a $110,000 income, $600 in monthly debts and $40,000 down at 6.5%, the 28% housing limit allows a payment of $2,566.67. After taxes, insurance and PMI, that supports a home of about $359,000.
Frequently asked questions
Is the amount a lender approves what I should spend?
Not necessarily. Approval limits ignore childcare, savings goals, commuting and other costs. Many buyers aim below the maximum on purpose.
What counts as monthly debt?
Minimum payments on car loans, student loans, credit cards, personal loans and child support. Rent, utilities and groceries do not count, though they matter for your own budget.
How does a bigger down payment help?
It lowers the loan amount and the monthly payment, and at 20% down on a conventional loan it removes PMI, which can raise the price you can afford.
Sources
- Consumer Financial Protection Bureau (CFPB): Buying a house
- CFPB: What is private mortgage insurance?
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