Monthly Affordability Calculator
“Can I afford it?” is really two questions: can you fit the monthly payment, and will a lender agree? Both come down to debt-to-income ratios. This monthly affordability calculator answers one narrow question only: given your income, your existing debts, and the DTI targets you choose, what is the maximum new monthly payment you can carry? It gives you a payment ceiling, not a home price, not a loan amount, and not an approval decision.
Quick Answer
With $7,500 monthly income and $800 of existing debts, a 36% back-end DTI allows $2,700 of total monthly debt, leaving $1,900 a month for a new payment. The 28% housing cap allows $2,100, so total debt is the binding constraint here, and you sit inside the 43% Qualified Mortgage ceiling with $2,425 of headroom to spare. That $1,900 is a ceiling, not a target: it is the most you can carry at the targets you set, not the amount you should spend.
The 28/36 rule in one minute
Front-end DTI is housing costs divided by gross monthly income. Back-end DTI adds every other recurring debt: car loans, student loans, credit card minimums, child support. The classic rule says keep the first under 28% and the second under 36%. On $7,500 a month, that is $2,100 for housing and $2,700 for all debts combined. The calculator runs both limits and reports the lower one as your ceiling, because a payment that passes one limit and fails the other still fails.
Three numbers in the result deserve a second look. Current back-end DTI shows where you stand before any new payment: $800 on $7,500 is 10.7%, so you are starting from a strong position. Income left after all debts shows what remains once every debt payment, including the new one at its ceiling, is paid: at 36%, that is $4,800, which still has to cover everything DTI ignores. Headroom to QM 43% shows how much more a lender operating at the legal ceiling could theoretically allow: $3,225 minus $800, or $2,425 here. That headroom is not extra spending money. It is the distance to a wall.
Front-end vs back-end: which binds you, and why it matters
Most borrowers assume housing is the constraint. Often it is the car loan and the student loans. In the worked example, the 28% housing cap allows $2,100 but existing debts leave only $1,900 of back-end room, so debt wins. Flip it: with zero existing debts, the full $2,700 of back-end room exceeds the $2,100 housing cap, and housing binds instead, giving a ceiling of $2,100. The calculator names the binding constraint because that tells you exactly which lever to pull: pay down debts, or accept a smaller housing payment.
This is also why the ceiling must be the lower of the two limits, not whichever one the tool happened to compute first. A tool that reports back-end room as the headline even when the housing cap is lower overstates what you can carry, by $600 a month in the zero-debt example above. Every competing tool that states the formula correctly uses the minimum of the two limits, and this calculator does the same: ceiling equals the smaller of back-end room (income times back-end target minus existing debts) and the front-end cap (income times housing target), floored at zero when debts already exceed the target.
One scope note, stated plainly: the front-end target here is a housing target. If the new payment is not housing, the front-end cap does not apply to it in the same way, and the honest ceiling is the back-end room alone. The tool still shows both figures so you can see which one is doing the work; set the housing target high or read the back-end room line when the payment is not housing. What this page will never do is convert the ceiling into a home price or a loan amount. That conversion needs a rate, a term, a down payment, taxes, insurance, and HOA, and each of those belongs to a different tool: our house loan affordability calculator and mortgage loan affordability calculator do that conversion, and approval for home loan calculator addresses the approval question itself.
What lenders actually allow in 2026
Program ceilings differ, and they move. Conventional loans through automated underwriting commonly reach 45 to 50% back-end with compensating factors like high credit scores and cash reserves. FHA loans sit around 43% standard with stretch potential higher. VA loans use a 41% benchmark but lean on residual income instead of a hard cap. The calculator defaults to the conservative 36% because it keeps the payment livable, not just approvable: slide it to 43% to see your legal maximum, then ask whether you would actually want to live there.
The CFPB’s debt-to-income explainer is the plain-English version of the same math, and its Qualified Mortgage guide lays out why 43% is the line: loans above it lose key legal protections, so lenders treat it as a wall. Note the badge in the result follows that same line, and it checks both sides: it warns when your chosen target exceeds 43%, and also when your existing debts alone already exceed 43% before any new payment. That is an official threshold, not a house verdict band, and the tool does not invent comfort grades between the two.
Turning the number into a decision
A $1,900 maximum is not a $1,900 target. Lenders approve payments; they do not pay them. Leave margin for the costs DTI ignores: maintenance, utilities, groceries, savings, and the emergency fund that keeps one bad month from becoming a missed payment. The borrowers who sleep well are usually the ones who qualified for far more than they spent. If the ceiling feels tight, the honest moves are paying down a debt before applying, which raises back-end room dollar for dollar, or lowering the housing target, which lowers the cap directly. Stretching the DTI target to make the answer bigger changes the arithmetic, not your bank account.
Before you commit to a payment near the ceiling, check how many months of expenses you could cover if income stopped: our same-batch months of expenses calculator answers that companion question. A ceiling you can carry and a reserve you can fall back on are two different kinds of safety, and you want both.
What competing calculators miss
Most affordability tools do one of two things that blur the question this page keeps sharp. Some jump straight from income to a home price, burying the payment ceiling inside rate, term, tax, and insurance assumptions you never chose. Others report a single ratio without naming which limit binds, so you cannot tell whether paying down a debt or shrinking the housing budget would help more. A few state the ceiling formula correctly in prose but report the wrong headline when the front-end cap binds, showing back-end room as the answer even though the housing cap is lower. This calculator reports the minimum of the two limits as the headline, names the binding constraint, and stops at the payment: no price, no loan amount, no approval verdict smuggled in.
Frequently Asked Questions
Up to $1,900 for a new payment with $800 of existing debts at 36% DTI: $7,500 times 36% is $2,700 of total debt room, minus $800 already committed. The 28% housing cap would allow $2,100, so total debt binds first and the ceiling is $1,900.
Front-end DTI is housing costs divided by gross monthly income. Back-end DTI is all monthly debt payments, including housing and every other recurring debt, divided by gross monthly income. Your ceiling is whichever limit gives the smaller payment.
Because the ceiling is the lower of two different calculations. Back-end room is total debt room minus debts you already carry; the front-end cap is a straight share of income. When debts are heavy, back-end room shrinks below the housing cap. When debts are light, the housing cap is the smaller number. The ceiling is always the smaller of the two.
Under CFPB Qualified Mortgage rules, a back-end DTI at or below 43% is one of the markers of a loan with key legal protections for the lender. Above 43%, the loan loses those protections, so most lenders treat 43% as a practical wall even where other programs allow higher ratios with compensating factors.
No, deliberately. A price needs an interest rate, a loan term, a down payment, property taxes, insurance, and HOA fees, none of which this tool asks for. Use the payment ceiling here, then convert it to a price with a house loan or mortgage affordability tool that asks for those inputs explicitly.
Lenders use gross, pre-tax income, so this calculator does too. But gross flatters the math: the payment comes out of take-home pay. Sanity-check any ceiling against your actual bank account before treating it as affordable in real life.
Recurring minimum payments: car loans, student loans, credit card minimums, personal loans, child support, and similar obligations. Count minimum payments, not balances. Do not count utilities, groceries, subscriptions, or everyday living expenses, even though they affect whether the ceiling feels livable.
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References
- What is a debt-to-income ratio?, Consumer Financial Protection Bureau, accessed October 2026.
- Qualified Mortgage standards, Regulation Z 1026.43, Consumer Financial Protection Bureau, accessed October 2026.
- Housing counseling program, U.S. Department of Housing and Urban Development, accessed October 2026.
- Loan Affordability Calculator, iotools.cloud, accessed October 2026.