28/36 Rule Calculator

Check your housing and total debt-to-income ratios against the 28/36 rule — a classic mortgage qualification guideline used by lenders and budgeting experts.

850.2K uses Updated · 2026-05-14 Runs locally · zero upload
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How to Use 28/36 Rule Calculator

The 28/36 Rule Calculator measures your housing affordability against a time-tested guideline.

  1. Enter gross monthly income — Use household pre-tax income.
  2. Enter total housing cost (PITI) — Principal, interest, taxes, insurance, HOA, and PMI.
  3. Enter other monthly debt payments — Auto loans, student loans, minimum credit card payments, alimony, etc.
  4. Read the result — The 28/36 Rule Calculator shows your housing ratio, total DTI, recommended maximums, and whether you pass.

Formula & Theory - 28/36 Rule Calculator

The 28/36 Rule Calculator uses two simple ratios:

HousingRatio = HousingCost / GrossMonthlyIncome
TotalDTI     = (HousingCost + OtherDebt) / GrossMonthlyIncome

MaxHousing   = 0.28 × GrossMonthlyIncome
MaxDebt      = 0.36 × GrossMonthlyIncome

The 28/36 rule has roots in Fannie Mae and Freddie Mac underwriting guidelines from the 1980s and 1990s. The front-end ratio (28%) limits housing burden; the back-end ratio (36%) limits total debt burden, including the mortgage.

Modern underwriting is more flexible. Qualified Mortgage (QM) rules under Dodd-Frank historically allowed DTI up to 43%, and many programs (FHA, VA, conventional with compensating factors) routinely approve DTIs of 45–50%. The 28/36 rule, however, remains the gold standard for personal budgeting — it leaves room for savings, retirement contributions, and emergency funds that aggressive DTIs can crowd out.

Compensating factors that can let you stretch beyond 28/36 include strong credit scores (760+), substantial cash reserves (6–12 months PITI), large down payment (20%+), and stable employment in a high-earning field.

Use Cases for 28/36 Rule Calculator

  • Home-buying readiness — Confirm a target home price won’t break the back-end ratio.
  • Refinance planning — Check whether refinancing a non-mortgage debt would free up enough DTI room.
  • Budget audits — Personal-finance teachers use the 28/36 rule as a benchmark for healthy household finances.
  • Pre-approval prep — Have your numbers ready before talking to a lender.
  • Career change planning — Test whether your housing cost remains affordable on a reduced salary.
  • Couple planning — Combine two incomes and existing debts before committing to a mortgage.

The 28/36 Rule Calculator turns a classic budgeting rule into a precise, actionable diagnostic in seconds.

Frequently asked questions about 28/36 Rule Calculator

What is the 28/36 rule?

The 28/36 rule says you should spend no more than 28% of gross monthly income on housing (PITI) and no more than 36% on total debt payments combined.

Why do lenders care about this ratio?

Conventional mortgage underwriting uses front-end (28%) and back-end (36%) DTI thresholds — though current programs often allow 43–50% DTI with compensating factors.

Does the 28/36 Rule Calculator include taxes and insurance?

Yes. Housing cost should include principal, interest, property tax, homeowners insurance, HOA dues, and PMI (collectively PITI).

Is my data stored?

No. All calculations happen in your browser; nothing is sent to a server.