28/36 Rule Calculator
The 28/36 rule calculator helps you compare a housing payment against the two debt-to-income checkpoints often used in mortgage planning. Enter gross monthly income, expected housing cost, and other debt payments to see your front-end ratio, back-end ratio, and the monthly limits implied by the rule.
How to use this calculator
Start with your household’s gross monthly income. That is income before taxes and payroll deductions, not take-home pay. Next, enter the monthly housing payment you want to test. For a homeowner or buyer, include principal, interest, property taxes, homeowners insurance, mortgage insurance, and HOA dues when they apply. For a renter, use rent plus any required monthly housing charges.
Finally, add other required monthly debt payments. Include auto loans, student loans, personal loans, credit card minimum payments, alimony, and similar obligations. Do not include flexible spending such as groceries, utilities, fuel, streaming subscriptions, or savings transfers; those expenses matter for your budget, but they are not usually part of the debt ratio calculation.
Use the result as a quick stress test. If the calculator shows a ratio above the guideline, try lowering the housing payment or reducing other debts to see which change has the biggest effect. To place the payment in your whole spending plan, compare the result with the budget calculator, mortgage calculator, and debt-to-income calculator.
How it works / what it means
The first half of the rule is the front-end ratio. It asks whether housing alone is reasonable compared with gross monthly income. A common target is <= 28%. The second half is the back-end ratio. It asks whether housing plus other required debt payments stay at <= 36% of gross monthly income.
Passing both checks suggests the payment may leave room for taxes, food, utilities, insurance, maintenance, savings, and emergencies. Failing one check does not automatically mean a loan is impossible, but it is a warning that the payment could be tight or that a lender may ask for compensating strengths.
Formula
The two ratios use monthly amounts:
The guideline limits are:
For example, a household earning $8,000 per month has a 28% housing limit of $2,240 and a 36% total debt limit of $2,880.
Example 28/36 rule checks
| Gross monthly income | Housing cost | Other debt | Front-end ratio | Back-end ratio | Result |
|---|---|---|---|---|---|
| $6,000 | $1,500 | $400 | 25% | 31.67% | Within guideline |
| $8,000 | $2,000 | $500 | 25% | 31.25% | Within guideline |
| $8,000 | $2,500 | $700 | 31.25% | 40% | Above both limits |
| $10,000 | $2,700 | $1,000 | 27% | 37% | Housing ok, total debt high |
Common mistakes/tips
- Using take-home pay instead of gross pay. The traditional ratio is based on pre-tax income.
- Forgetting property taxes, homeowners insurance, mortgage insurance, or HOA dues when estimating a mortgage payment.
- Treating 28/36 as a complete budget. You still need cash for repairs, moving costs, savings, and irregular bills.
- Ignoring other debt. A car payment or credit card minimum can be the difference between passing and failing the back-end test.
- Assuming every lender uses the same cutoff. Loan programs vary, so use this as a planning screen before getting personalized quotes.