About the 28/36 Rule Calculator
This 28/36 rule calculator measures the two ratios mortgage lenders use to judge affordability. The front-end ratio, also called the housing expense ratio, is your total monthly housing payment divided by gross monthly income. The back-end ratio adds every other monthly debt payment — car loans, student loans, credit card minimums — to that housing payment.
The classic guideline is a front-end ratio of 28% or less and a back-end ratio of 36% or less. Enter your income, your expected housing payment (principal, interest, taxes, insurance, PMI and HOA) and your other debts to see where you stand and how much housing payment you could carry before hitting either limit.
Many loan programs allow higher ratios — FHA and conventional loans with automated underwriting often approve back-end ratios in the 40s — so you can change both limits. Staying near 28/36 still leaves more room for savings and surprises.
With the default inputs, the front-end (housing) ratio is 26.3%. Change any value above to recalculate instantly.
How to use the 28/36 rule calculator
- 1Enter your household’s gross annual income.
- 2Enter the full monthly housing payment, including taxes, insurance and HOA.
- 3Add the minimum monthly payments on all other debts.
- 4Adjust the limits if your loan program allows higher ratios.
- 5Check the result and the maximum housing payment you can carry.
Formula and method
Divide annual gross income I by 12 to get monthly income. The front-end ratio compares the full monthly housing payment H — principal, interest, property tax, insurance, mortgage insurance and HOA — to that income. The back-end ratio adds recurring debt payments D.
The maximum housing payment is whichever limit binds first: the front-end limit f times income, or the back-end limit b times income minus existing debts. Lenders use gross (pre-tax) income, which is why take-home budgets often feel tighter than the ratios suggest.
- H
- Monthly housing payment (PITI + HOA)
- D
- Other monthly debt payments
- I
- Gross annual income
- f, b
- Front-end and back-end limits (28% and 36%)
Worked examples
$96k income, $2,100 housing, $600 debts
Monthly income is $8,000. Housing of $2,100 is 26.25% and total debt of $2,700 is 33.75%, both within 28/36. The front-end limit ($2,240) binds, leaving $140 of room.
Stretching on a $72k income
On $6,000 a month, a $2,200 payment is 36.7% of income and total debts reach 48.3%. Because $700 of debts eat into the $2,160 back-end limit, the maximum housing payment is $1,460 — $740 less than planned.
High income, low debt
At $12,500 a month, a $3,000 payment is 24% and total debts are 27.2%. The front-end limit of $3,500 allows $500 more per month.
Frequently asked questions
What is the 28/36 rule?+
It is a lending guideline that says your housing costs should be no more than 28% of gross monthly income, and all monthly debt payments including housing no more than 36%.
What counts as housing expense in the front-end ratio?+
Principal and interest, property taxes, homeowners insurance, mortgage insurance (PMI or FHA MIP) and HOA or condo dues. Utilities and maintenance are not included.
Can I get a mortgage with a back-end ratio over 36%?+
Often, yes. Conventional loans run through automated underwriting can approve debt-to-income ratios up to about 50% with strong credit and reserves, and FHA loans frequently allow ratios in the mid-40s or higher.
Do lenders use gross or net income?+
Lenders use gross monthly income, before taxes and deductions. Self-employed borrowers typically use net business income from tax returns averaged over two years.
What is the difference between front-end ratio and DTI?+
The front-end ratio counts only housing costs. Debt-to-income (DTI), or the back-end ratio, counts housing plus all other recurring debt payments, and is the ratio lenders weigh most heavily.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.