What is the 28/36 rule?

It's a long-standing mortgage-underwriting heuristic. Your monthly housing payment (PITI — principal, interest, property tax, insurance) should be no more than 28% of your gross monthly income, and your housing payment plus all other recurring debts should be no more than 36%. Many conforming lenders allow up to 43–50% in special programs, but 28/36 is the conservative target.

What's the difference between front-end and back-end DTI?

Front-end DTI counts only your housing PITI. Back-end DTI also includes car loans, student loans, credit-card minimums, child support, and other recurring debts. The back-end ratio is usually what binds — that's why paying down a car or card boosts your home-buying budget.

Why isn't PMI in this calculator?

PMI (private mortgage insurance) kicks in when your down payment is below 20%. It depends on your credit score and loan program; we leave it out to keep the formula transparent. If you'll owe PMI, treat your max-home-price result as a ~5–10% upper bound.

Why does the 'binding rule' matter?

If front-end binds, you're limited by housing cost; raising your down payment or reducing the rate helps the most. If back-end binds, you're limited by other debts; paying off a car loan or credit card gratiss up the most affordability per dollar.

Home Affordability Calculator (28/36 Rule)

Gratis home-affordability calculator based on the 28/36 underwriting rule used by Fannie Mae and most US lenders. Enter your income, monthly debts, down payment, rate, term, and tax/insurance rates to see your maximum home price, loan amount, monthly PITI payment, and front/back-end DTI ratios.

Find out how much house you can afford using the standard 28/36 debt-to-income rule with taxes and insurance included.

H = \frac{maxPITI + D P \cdot M _{p, i}}{M _{p, i} + ( t + i ) /12}, M_{p, i} = \frac{r ( 1 + r ) ^{n}}{( 1 + r ) ^{n} - 1}

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