Your debt-to-income ratio: the rules that change the number

Lenders count the minimum monthly payments on the debts in your credit report, plus the new loan’s payment, and divide that total by your gross monthly income. They ignore most of what you actually spend to live: groceries, utilities, childcare, phone bills and savings. How high the result can go depends on the loan. For a conventional mortgage run through Fannie Mae’s automated system it can reach 50%, while the old 43% rule for qualified mortgages no longer applies.

How the ratio is calculated

The CFPB’s definition is plain: your debt-to-income ratio (DTI) is all your monthly debt payments divided by your gross monthly income. Gross means before taxes, health insurance and retirement contributions, so $6,000 a month in salary counts as $6,000 even if $4,500 reaches your account.

Mortgage lenders compute two versions. The front-end ratio is the proposed housing payment alone: principal, interest, property taxes, homeowners insurance and any HOA dues or mortgage insurance. The back-end ratio adds every other debt payment to that. When a lender quotes a DTI limit, it nearly always means the back-end figure.

What counts, and the rules that change the number

The debts come mostly from your credit report, but mortgage guidelines adjust several of them. These are Fannie Mae’s rules, from section B3-6-05 of its Selling Guide, unless noted.

• Housing. When you buy, your current rent drops out and the proposed payment replaces it. If you keep a home you already own, its payment stays in.
• Credit cards. The required minimum payment counts, not what you actually pay. If the report shows no minimum and nothing documents a lower amount, the lender must use 5% of the balance.
• Installment loans. Car loans, personal loans and the like count if more than 10 monthly payments remain. With 10 or fewer left, the lender may leave the debt out unless it significantly affects your ability to pay. Lease payments always count, however few months remain.
• Student loans. If your credit report shows a payment above zero, the lender can use it. Fannie Mae accepts a documented $0 income-driven payment. Freddie Mac and FHA use 0.5% of the balance when the report shows zero, unless documentation supports a different amount, which on a $40,000 balance means $200 a month. For loans in deferment or forbearance, Fannie Mae uses 1% of the balance or a fully amortizing payment.
• Debts someone else pays. If you co-signed a loan that the other person pays, the lender can exclude it with the most recent 12 months of canceled checks or bank statements from that person showing no late payments. Without that proof, it counts as yours. The full picture is in what cosigning means for you.
• Court-ordered payments. Alimony and child support you pay count as debts.

Lenders outside mortgages, such as personal loan and card issuers, set their own formulas and limits, and their applications commonly ask for your rent or housing payment.

What the ratio leaves out

Nothing in the formula sees your daily costs: food, utilities, gas, car insurance and repairs, phone and internet, medical bills, childcare, income taxes and retirement savings. Property taxes and insurance count only when they are part of a mortgage payment.

Childcare shows the gap most clearly. A family paying $2,000 a month for daycare and a family paying nothing can have the same DTI and get the same approval. So a ratio the lender accepts tells you the loan fits its rules, not that it fits your budget. Run your own numbers with every expense before you take the maximum you are offered.

How high lenders let it go

The 43% figure many people still quote came from the CFPB’s original Qualified Mortgage rule. The revised General QM rule replaced that cap with a test based on the loan’s price, and it has been mandatory for applications since October 1, 2022. Lenders must still consider your DTI or residual income, but no federal rule sets 43% as the ceiling.

A worked example

Say you earn $6,000 a month before taxes and apply for a mortgage with a proposed payment of $1,800, including taxes and insurance. You also have a $450 car payment, a $150 student loan payment, a $4,000 card balance with a $120 minimum, and a personal loan with a $150 payment and 14 payments left, about $1,974 still owed.

• Front-end ratio: $1,800 divided by $6,000 is 30%.
• Back-end ratio: $2,670 in total payments divided by $6,000 is 44.5%.

That passes Fannie Mae’s automated limit but sits above the 43% FHA manual threshold. Now suppose you have about $2,000 in savings to bring it down. Paying off the personal loan removes its $150 and drops the ratio to 42%. Putting the same $2,000 on the card cuts its minimum, if the issuer charges 1% of the balance plus interest at a rate of 24%, from $120 to $60, which only gets you to 43.5%. Waiting four months gets you 42% too: with 10 payments left, the personal loan can drop out under Fannie Mae’s rule without you paying it off.

The general lesson is that dollars aimed at a small installment loan you can clear move the ratio more than dollars spread over a large card balance, because a card minimum shrinks only a few percent of what you pay.

Before you apply

1. Pull your reports free at AnnualCreditReport.com and dispute any debt that is not yours or is shown as open after you paid it off. The FTC explains how in disputing errors on your credit reports.
2. Check the payment each student loan shows on the report. If it is $0 or missing, get a letter or statement from your servicer with your actual payment.
3. If someone else pays a loan you co-signed, collect 12 months of their canceled checks or bank statements now.
4. Document all your income, including side work, alimony received or rental income; lenders often want two years of tax returns for self-employment income.
5. Do not open new credit or finance a car between preapproval and closing. A new payment can push a borderline ratio over the limit.