Home Affordability Calculator

Home Affordability Calculator answers the question every buyer starts with: how much house can I actually get? Instead of taking a price and returning a payment, it works backwards from the debt-to-income limits lenders apply. Your income sets two ceilings — the front-end rule capping housing costs at 28% of gross monthly income, and the back-end rule capping all debt at 36% — and the lower of the two becomes your housing budget. From there the tool solves algebraically for a maximum price, which is necessary because property tax scales with the price you are trying to find. Insurance, HOA fees and your down payment are all part of the equation, and the output includes a full monthly breakdown plus a note saying which DTI rule limited you, so you know whether paying down debt or raising income moves the number.

Key Features

• Solves for Price, Not Payment

  Works backwards from DTI limits to a maximum home price. Property tax depends on price, so this needs algebra rather than a simple payment formula.

• Both DTI Rules Applied

  Front-end (28% housing) and back-end (36% total debt) ceilings are both calculated and the tighter one wins, exactly as underwriting works.

• Adjustable DTI Thresholds

  Both percentages are editable, so you can model an FHA-style 31/43 or a conservative 25/33 rather than being locked to one rule.

• Complete Housing Cost Model

  Includes principal, interest, property tax, insurance and HOA. Leaving tax and insurance out is how buyers end up over-committed.

• Limiting Factor Explained

  States whether the front-end or back-end rule capped you. If back-end is binding, clearing other debt raises your budget more than a bigger deposit.

• Down Payment Percentage

  Shows your deposit as a percentage of the resulting price, which is what decides mortgage insurance and rate tiers.

1. 1

   Enter income and monthly debts

   Use gross annual income and the total minimum monthly payments on all other debts.

2. 2

   Enter your down payment

   The cash you have available. It raises the price you can reach without raising the monthly payment.

3. 3

   Set rate and term

   Use a current quoted mortgage rate and your intended term — 30 years buys more house, 15 years costs far less interest.

4. 4

   Add tax, insurance and HOA

   Property tax rate varies enormously by location, so use a local figure rather than the default.

5. 5

   Review the price and breakdown

   Check the maximum price, then the monthly breakdown, then the note explaining which DTI rule limited you.

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