Debt-to-Income Ratio Calculator
Front-end and back-end ratios against the 28/36 rule, showing which of the two limits actually binds — because it is not always the same one.
Gross means before tax. Other debts means the minimum monthly payments on cards, car and student loans — not groceries or utilities, which lenders do not count here. 28/36 is a convention rather than a law, and real programmes vary widely. Nothing is uploaded.
The 28/36 rule is two rules, and they trade places
On $6,000 a month the housing rule allows $1,680, flat, whatever else you owe. The total rule allows $2,160 minus your other debts — so it only starts to bite once those pass $480, which is exactly the gap between the two percentages. Below that the 28% rule decides and the 36% one is slack; above it they swap.
| Other debts | Housing rule allows | Total rule allows | Which binds | Your budget |
|---|---|---|---|---|
| $0 | $1,680 | $2,160 | the 28% rule | $1,680 |
| $200 | $1,680 | $1,960 | the 28% rule | $1,680 |
| $400 | $1,680 | $1,760 | the 28% rule | $1,680 |
| $480 | $1,680 | $1,680 | the 28% rule | $1,680 |
| $600 | $1,680 | $1,560 | the 36% rule | $1,560 |
| $800 | $1,680 | $1,360 | the 36% rule | $1,360 |
| $1,200 | $1,680 | $960 | the 36% rule | $960 |
| $1,800 | $1,680 | $360 | the 36% rule | $360 |
At the crossover itself the two allowances are identical, which is what makes it the crossover. The practical version: if you have meaningful other debts, the 28% figure everyone quotes is not your constraint and working it out tells you nothing useful.
Above the crossover, a dollar of debt costs a dollar of house
Once the total rule is the binding one, the exchange rate is exactly one to one — a $400 car payment removes $400 a month of housing budget, and clearing it hands the whole $400 back. Below the crossover the exchange rate is zero: the housing rule is already the constraint, so paying off a small loan buys you nothing at all in borrowing terms. Which of those two worlds you are in is the first thing to establish, because it decides whether clearing a debt before applying is worth doing.
Why there are two ratios at all
The front-end ratio counts housing against income; the back-end ratio counts housing plus every other debt payment. The second can never come out below the first, since it counts strictly more, and the two coincide only when there is nothing else owed. They exist separately because they answer different questions — one asks whether the house is affordable, the other whether it is affordable as well as everything else. A household at $1,500 housing and $700 of other debts on $6,000 sits at 25.0% and 36.7%: comfortably inside the first and over the second. Reporting only the first would have called that fine.
How to use
- Enter gross monthly income, housing costs and other debt payments.
- Read both ratios against their limits.
- See which of the two rules is the one constraining you.
- Adjust the limits if your lender uses different ones.
Frequently asked questions
What is the 28/36 rule?
Two separate limits. The front-end rule caps housing costs at twenty-eight per cent of gross monthly income. The back-end rule caps housing plus every other recurring debt payment at thirty-six per cent. Both have to be satisfied, and which one actually constrains you depends on what else you owe.
Which of the two limits binds?
Whichever allows less. On six thousand a month the housing rule allows a flat $1,680 whatever else you owe, while the total rule allows $2,160 minus your other debts. So the total rule only starts to bite once those debts pass $480 — exactly the gap between the two percentages. Below that the 28% figure decides; above it, the 36% one does.
Will paying off a car loan let me borrow more?
Only if the back-end rule is the one binding you. Above the crossover the exchange rate is one for one — clearing a $400 payment hands back $400 a month of housing budget. Below it, the housing rule is already your constraint and clearing a small debt moves your budget by nothing at all.
What counts as debt here?
The minimum monthly payments on cards, car loans, student loans and similar recurring obligations. Groceries, utilities, phone bills and insurance other than what is bundled into housing are generally not counted, which is why this ratio can look comfortable while a budget does not.
Gross or net income?
Gross — before tax. That is a meaningful difference, because the ratio is measured against money you never actually receive. A household at the limit on gross income is spending a noticeably larger share of what lands in the account.
Why are there two ratios rather than one?
They answer different questions: whether the house is affordable, and whether it is affordable as well as everything else. The back-end figure can never come out below the front-end one, since it counts strictly more, and the two coincide only when nothing else is owed. Reporting only the first would call a household at 25% housing and 36.7% total perfectly fine.
Are these limits fixed?
No, they are a convention rather than a rule, and real programmes vary widely — some allow considerably higher back-end ratios with compensating factors. Both limits are editable here so you can put in whatever numbers you have been given.
Does this send anything anywhere?
No. Every figure is computed in your browser, and nothing is uploaded or stored.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.