What this calculator does
The 28/36 rule is a widely used mortgage affordability guideline: housing costs should not exceed 28% of gross monthly income, and total debt payments, housing included, should not exceed 36%. Lenders use versions of these ratios to gauge how much a borrower can comfortably repay, and the same thresholds work as a quick personal check before shopping for a loan.
The two numbers serve different purposes. The 28% housing figure looks at the mortgage payment on its own, while the 36% total debt figure adds in car loans, student loans, credit cards and any other regular debt repayments. A household can pass the housing test and still fail the total debt test if other repayments are high, which is why both figures are worth checking rather than just the housing one. Lenders vary in exactly which thresholds they apply, so both percentages here are free to edit.
The formula
The maximum housing payment is gross monthly income multiplied by the housing threshold, and the maximum total debt payment is gross monthly income multiplied by the total debt threshold. Subtracting other debt payments from the total debt limit shows how much of that allowance is left for housing specifically.
| Term | Meaning |
|---|---|
| Housing threshold | The maximum share of gross income recommended for housing costs, traditionally 28%. |
| Total debt threshold | The maximum share of gross income recommended for all debt payments combined, traditionally 36%. |
| Gross monthly income | Income before tax and other deductions, the base the two percentages are applied to. |
The inputs explained
| Field | What to enter |
|---|---|
| Gross monthly income ($) | Gross monthly income, before tax and other deductions. |
| Housing payment threshold (%) | The housing cost threshold to apply, traditionally 28%, though some lenders use a different figure. |
| Total debt payment threshold (%) | The total debt payment threshold to apply, traditionally 36%, though some lenders use a different figure. |
| Other monthly debt payments ($) | Any regular monthly debt repayments other than housing, such as car loans, credit cards or student loans. |
When to use it
Working out a target house payment before shopping
Before looking at properties or getting pre-approved, applying the 28% threshold to gross income gives a starting figure for what a lender is likely to consider affordable.
Checking whether other debts are eating into borrowing capacity
Entering existing car loan, credit card or student loan repayments shows how much of the 36% total debt allowance is already used up before housing is even considered.
Comparing a lender's own thresholds
Some lenders use different figures, such as 25/33 or 31/43. Editing both thresholds lets the same income be checked against whichever guideline a particular lender applies.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Maximum housing and total debt payments at different incomes
The standard 28/36 thresholds applied across a range of gross monthly incomes.
| Gross monthly income | Maximum housing payment | Maximum total debt payment |
|---|---|---|
| $5,000 | $1,400.00 | $1,800.00 |
| $6,000 | $1,680.00 | $2,160.00 |
| $7,000 | $1,960.00 | $2,520.00 |
| $8,000 | $2,240.00 | $2,880.00 |
| $10,000 | $2,800.00 | $3,600.00 |
| $12,000 | $3,360.00 | $4,320.00 |
How a stricter or looser threshold changes the housing limit
The same $8,000 income with the housing threshold varied.
| Housing threshold | Maximum housing payment |
|---|---|
| 25% | $2,000.00 |
| 26% | $2,080.00 |
| 28% | $2,240.00 |
| 30% | $2,400.00 |
| 31% | $2,480.00 |
| 33% | $2,640.00 |
Questions
Are 28% and 36% fixed rules lenders always follow?
No. They are a common guideline, not a legal requirement, and actual lending decisions depend on the specific lender, loan type, credit history and other factors. Some lenders use different thresholds entirely.
Does the total debt figure include the housing payment?
Yes. The 36% total debt threshold is meant to include housing costs alongside all other debt repayments, not sit on top of them. This calculator shows the total debt limit and how much of it remains for housing after other debts.
What counts as a housing cost for the 28% figure?
Typically the mortgage principal and interest payment, plus property taxes and insurance where applicable. Check exactly what a specific lender includes, since definitions vary.
What if my other debts already exceed the total debt limit?
It means the total debt threshold is already used up, or exceeded, before housing is added, which most lenders would treat as a sign to reduce other debt first or reconsider the loan amount.
For a fuller picture of borrowing capacity including a specific loan term and rate, see the debt-to-income ratio calculator and the how much can I borrow calculator.