Two divisions, and nothing else
Affordability on this page is a ratio, not a yes. Housing share is the monthly housing payment you type divided by gross monthly income. Debt-to-income adds the other monthly debt payments you type, then divides by the same income. Gross means before taxes. If income is $8,000.00, a housing payment of $1,800.00 is a housing share of 22.50 percent. Add $400.00 of other debts and the debt-to-income ratio is 27.50 percent. Those percentages are the inputs. Change the inputs and the percentages move. Nothing in the file looks up your pay stub.
The CFPB's 2026 edition of Your Home Loan Toolkit tells a reader to estimate the percentage of total monthly income that goes to the total monthly home payment. It then says a mortgage lending rule of thumb is that the total monthly home payment should be at or below 28 percent of total monthly income before taxes. The next sentence matters as much as the 28: lenders might approve you for more or for less depending on your overall money picture. This page puts 28 percent of the income you typed on the screen so you can see the gap. On $8,000.00 of gross monthly income, 28 percent is $2,240.00. The housing payment of $1,800.00 sits $440.00 under that line. Being under the line is not an approval. Being over it is not a denial.
What the toolkit counts as the home payment
The toolkit's step is about the total monthly home payment, not principal and interest alone. A payment a servicer collects often includes taxes and insurance. Mortgage insurance can be in it too. This form does not build that payment for you. The mortgage calculator does principal and interest. The down-payment page shows when a conventional loan is under the CFPB's 20 percent line, where private mortgage insurance may be required. If you want those dollars inside the housing share, add them yourself and type the sum. Leaving them out makes the share look smaller than the payment you would actually send.
Other debts, on a debt-to-income ratio, are the monthly payments you already owe: an auto loan, a student loan, a card minimum if you choose to count it. The CFPB's money-goals worksheet, an older Bureau tool, says court-ordered payments such as child support can count as debt for that exercise, and that gross monthly income is income before taxes or insurance. This page will not guess which of your bills belong. If you leave other debts at zero, the debt-to-income ratio equals the housing share, which is a different question from a household that already has a car payment.
The principal number is a payment run backwards
The last figure asks a separate question: if the housing budget were exactly 28 percent of income, and if that entire budget were principal and interest at the rate and term you typed, how large a loan would that payment support? At 6 percent for 30 years, a payment of $2,240.00 supports about $373,613.22. Six percent is the same round rate the rest of this site uses so the payment formula can be checked. It is not a rate a lender is offering. The inverse of the site's checked payment, $1,199.10 at 6 percent for 360 months, comes back to $199,999.82, a few cents under $200,000.00, because that payment was rounded to the cent before it was inverted.
That principal is not a purchase price. A purchase price includes a down payment and excludes nothing you still have to pay every month. Taxes and insurance were not in the 28 percent payment when it was treated as pure principal and interest. If part of the 28 percent has to cover taxes, the loan that fits is smaller. The rent-versus-buy page is where a price, a down payment, and a stay sit next to rent. This page stops at the ratios and the one inverted payment.
Qualified mortgages are no longer a 43 percent test
People still repeat 43 percent as if it were the legal ceiling on debt-to-income. The CFPB's general qualified-mortgage definition used to include a 43 percent cap. The Bureau removed that cap and replaced it with limits based on the loan's price. A qualified mortgage still has to avoid certain risky features, stay inside points-and-fees limits, and come with a lender that considered and verified income or assets and debts. The lender considers either the debt-to-income ratio or residual income. Considering a ratio is not the same thing as refusing every file above a number this website prints. This calculator does not know the annual percentage rate, the points, or the residual income, so it cannot say whether a loan would be a qualified mortgage.
Ability to repay is the lender's determination, made before the loan, with the documents the lender asks for. A ratio you compute at a kitchen table is a way to see how large the payment is next to income. It is not the determination. Giuseppe Ilarda, the site owner, writes and checks this page. He does not decide what you can afford. The disclaimer says the site does not give financial advice, and this ratio is part of that limit rather than an exception to it.
How to read a result that looks comfortable
A housing share under 28 percent can still be tight if the income is uneven, if the housing payment you typed left out taxes, or if the other debts are about to reset. A share over 28 percent can still be a loan a lender makes. The toolkit says both of those things by saying lenders might go higher or lower. Use the room-under-28 line as a distance, not a grade. Then open the mortgage calculator if you want the schedule, and the payoff calculator if you want to see what an extra principal payment does to the interest. None of those pages stores the income you typed. The arithmetic stays in the browser.