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Mortgage Affordability by DTI Calculator

Find the mortgage you qualify for from your income, existing debts and a maximum debt-to-income ratio — the way lenders actually size a loan.

Gross monthly income

Maximum DTI ratio

Existing monthly debt payments

Monthly property tax + insurance

Interest rate

Loan term

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How it works

Max total debt = income × DTI% · Housing budget = max total debt − existing debts · P&I budget = housing budget − tax & insurance · Loan = P&I × (1 − (1 + i)⁻ⁿ) ÷ i, i = rate ÷ 12

Lenders cap your total monthly debt at a share of gross income — the back-end DTI ratio, often around 43%. Subtracting the debts you already carry and the monthly escrow for taxes and insurance leaves what can go toward principal and interest, and that payment is worked backward through the mortgage formula into a loan amount. Because taxes and insurance are carved out first, a high-tax area shrinks the loan you qualify for even when income is unchanged.

Worked example

With $8,000/mo income and a 43% DTI, total debt is capped at $3,440. Subtract $500 of existing debts and $400 of tax + insurance, leaving $2,540 for principal and interest. At 6.5% over 30 years that payment supports roughly a $401,800 loan.

Frequently asked questions

What is a back-end DTI ratio?

It is all of your monthly debt payments — the new housing payment plus car loans, student loans and credit-card minimums — divided by gross monthly income. Many conventional loans cap it near 43%, though some programs allow more with strong compensating factors.

Why subtract taxes and insurance before computing the loan?

Your DTI limit applies to the full housing payment (PITI: principal, interest, taxes, insurance). Only the principal-and-interest slice buys loan balance, so escrow for taxes and insurance must come out of the budget first — which is why high-tax areas qualify for smaller loans.

Is the maximum loan the same as what I should borrow?

No. This is the ceiling a DTI rule allows, not a comfortable budget. Leaving room below the maximum protects you against rate resets, maintenance and income shocks.

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Work backward from the monthly housing payment you can afford to the home price it buys — accounting for down payment, rate, taxes and insurance.

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Estimate the cash to close on a home — lender fees, points, title, government fees, prepaids, escrow and FHA, VA or USDA upfront fees — as a quick estimate or line by line, with seller credits and earnest money.

Educational estimate, not financial, tax or lending advice. Confirm figures with your lender, agent or a qualified professional.