How this calculator works
The 28/36 rule is a long-standing lending guideline, not a legal limit. It says a household should spend no more than 28% of gross monthly income on housing and no more than 36% on all debt payments combined. The calculator divides each group by gross income so you can see how much room remains. Some lenders use a total debt ratio of 41% or more, and government-backed programs apply their own rules. The guideline deliberately ignores taxes, childcare and living costs, so it is a starting point rather than a budget.
Formula
Front-end ratio = housing cost / gross monthly income. Back-end ratio = (housing cost + other debt payments) / gross monthly income. Housing allowance = 0.28 × gross monthly income. Debt allowance = 0.36 × gross monthly income. Remaining room is each allowance minus the matching current payment.
Worked example
With $8,000 of gross monthly income, $2,000 of housing cost and $600 of other debt, the front-end ratio is 25% and the back-end ratio is 32.5%. The 28% housing allowance is $2,240, leaving $240 of room; the 36% debt allowance is $2,880, leaving $280 of total room. Both ratios pass, so the result reports that the limits are met.
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Frequently asked questions
Should I use gross or net income?
Lenders measure these ratios against gross income, before income tax and other deductions. A budget built on take-home pay will feel tighter than the ratio suggests.
What counts as other debt?
Include required monthly payments on credit cards, car loans, student loans and lines of credit. Living costs such as groceries, utilities, childcare and savings are not debt payments and are excluded from the 36% test.
Is passing the rule a guarantee of approval?
No. Lenders also assess credit history, down payment, employment, reserves and the property. The rule is a quick sanity check, not an underwriting decision.
Does the rule suit every household?
No. A single-income household or one with high fixed costs may be safer well below 28/36, while a household with large reserves may reasonably exceed it. Treat the result as one input to your own budget.