Mortgage Debt-to-Income Qualification Calculator

Estimates the maximum mortgage loan amount you can qualify for based on your income, existing debts, and standard lender DTI limits. Useful before you start house hunting.

Last updated: September 2026

Gross Monthly Income ($)

Monthly Debt Payments ($)

Interest Rate (%)

Loan Type

Monthly Property Tax ($)

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Formula below · 2 sources (CFPB, Wikipedia) · Updated Sep 2026

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About this calculator

Lenders evaluate affordability with two debt-to-income (DTI) ratios. The front-end ratio caps housing costs as a share of gross monthly income, and the back-end ratio caps housing plus all other monthly debts. The Loan Type sets the standard guideline pair: conventional 28% / 36%, FHA 31% / 43%, USDA 29% / 41%, and VA a single 41% total-DTI guideline (VA has no front-end ratio and also applies a residual-income test). The maximum housing payment is the smaller of (gross monthly income × front ratio) and (gross monthly income × back ratio − monthly debts). Property tax comes out of that housing budget, leaving the principal-and-interest payment, which is converted to a loan amount with the present-value-of-annuity factor: L = maxP&I × [(1+r)ⁿ − 1] / [r × (1+r)ⁿ], where r = interest rate / 12 / 100 and n = 360 months. Homeowner's insurance, PMI or MIP, and HOA dues are not subtracted, so subtract their monthly total from the property tax figure for a tighter estimate. Automated underwriting can approve higher ratios for strong files, so treat these as standard guidelines rather than hard limits.

How to use

Gross income = $7,000/month, existing debts = $400, interest rate = 6.8%, VA loan (41% total DTI), property tax = $250/month. Step 1 — Max housing payment = $7,000 × 0.41 − $400 = $2,470 (VA has no front-end limit). Step 2 — Subtract property tax: $2,470 − $250 = $2,220 for principal and interest. Step 3 — Monthly rate r = 6.8 / 100 / 12 = 0.005667; n = 360; PV annuity factor = [(1.005667)³⁶⁰ − 1] / [0.005667 × (1.005667)³⁶⁰] ≈ 153.39. Step 4 — Max loan = $2,220 × 153.39 ≈ $340,530. Add your down payment to find your maximum purchase price (e.g. 20% down → home price ≈ $340,530 / 0.80 ≈ $425,660). Switch to Conventional (28% / 36%): the front-end limit $7,000 × 0.28 = $1,960 is below the back-end limit $7,000 × 0.36 − $400 = $2,120, so the housing budget is $1,960, P&I is $1,710, and the max loan drops to about $262,300.

Frequently asked questions

What debt-to-income ratio do I need to qualify for a mortgage?

Most conventional lenders require a back-end DTI (all monthly debts including the new mortgage) at or below 43–45%. Fannie Mae's automated underwriting will sometimes approve loans up to 50% DTI for borrowers with strong compensating factors such as large cash reserves or excellent credit. FHA loans allow up to 50% DTI more readily. The lower your DTI, the more likely you are to receive the best interest rates and terms.

How do monthly debt payments affect how much mortgage I can qualify for?

Every dollar of existing monthly debt — car loans, student loans, credit card minimums — directly reduces the payment budget available for a mortgage. For example, a $400/month car payment on a $7,000 income at a 43% DTI reduces your available mortgage payment by $400, which can cut your maximum loan amount by $50,000 or more. Paying down or eliminating debts before applying can significantly increase your purchasing power. Even removing a small recurring debt improves your qualification ceiling.

Why does the lender use gross income instead of take-home pay when calculating DTI?

Lenders use gross (pre-tax) income because it is a consistent, verifiable figure documented on pay stubs, W-2s, and tax returns. Take-home pay varies widely based on withholding elections, retirement contributions, and benefit deductions that the borrower controls and can change. Using gross income creates a standardized comparison across all applicants. It does mean your actual budget will feel tighter than the DTI numbers suggest, since you pay taxes and other withholdings from the gross figure before any mortgage payment is made.