How to Calculate Debt-to-Income Ratio for a Mortgage

To calculate your debt-to-income ratio for a mortgage, add up your total monthly debt payments (including the mortgage payment you’re planning to take on), divide that sum by your gross monthly income, and multiply by 100. If you earn $6,000 a month before taxes and your total monthly debts including the proposed mortgage come to $2,000, your DTI is 33.3 percent. Federal law requires mortgage lenders to make a reasonable, good-faith determination that you can repay a loan before approving it, and DTI is one of the central measurements they use to make that call.¹

Which Monthly Payments Go on Top

The numerator is your total monthly debt. Lenders count recurring obligations that appear on your credit report: minimum credit card payments, auto loans, student loans, personal loans, and any mortgage payments on other properties you own. They also count legally required payments that may not show on a credit report, like court-ordered child support or alimony, when those payments have more than ten months left to run.²

Everyday living expenses do not count. Utilities, groceries, cell phone plans, car insurance, and streaming subscriptions stay out of the calculation because they aren’t fixed debt obligations tied to a repayment agreement.

For credit cards, use the minimum payment shown on the statement, not the full balance. For installment loans, use the scheduled monthly payment. And remember to include the proposed new mortgage payment itself, principal and interest along with property taxes, homeowners insurance, and mortgage insurance if any of those apply.

What Counts as Gross Monthly Income

The denominator is your gross monthly income, meaning what you earn before taxes, Social Security, health insurance, or retirement deductions come out. Lenders verify this figure through W-2s, tax returns, or payroll statements rather than taking your word for it.³

Base salary or hourly wages form the foundation. Overtime, bonuses, and commissions can be added when you can document a stable history of receiving them. Non-employment income like Social Security, pension payments, and alimony can count when you can show it will continue for the foreseeable future.⁴

Self-Employment Income

If you work for yourself, lenders generally want two years of federal tax returns, both personal and business, to establish an income history. They look at year-to-year trends in gross revenue, expenses, and taxable income to judge whether earnings are stable or declining. If your income dropped meaningfully from one year to the next, expect the lender to use the lower figure or ask for an explanation.⁵

A shorter history is sometimes acceptable. With at least 12 full months of self-employment income on your most recent return, some lenders will consider it if you can document prior experience or income in the same line of work. If the business has operated at least five years and you’ve held 25 percent or greater ownership throughout, one year of returns may be enough.⁵

Rental Income

If you own rental property, lenders typically count only 75 percent of the gross monthly rent as income. The other 25 percent is assumed to cover vacancy and maintenance. A property renting for $2,000 a month gives you $1,500 in usable income for the calculation.⁶

How Student Loans Get Counted

Student loans are worth pulling out separately because the payment your lender uses may not match what you actually pay. If your credit report shows a monthly payment above zero, the lender uses that number. If the reported payment is zero because you’re on an income-driven plan, the treatment splits by loan type.

For conventional loans sold to Fannie Mae, the lender can qualify you using the $0 payment shown on the report as long as they obtain documentation confirming the income-driven payment is genuinely zero.² FHA is stricter. If the credit report payment is zero, the lender must use 0.5 percent of your outstanding balance as the assumed monthly payment. On a $40,000 balance, that puts $200 a month on your debt side even when you’re paying nothing.⁷

Two Ratios, Not One: Front-End and Back-End

Lenders actually calculate two versions of the ratio. Same formula, different slices.

The front-end ratio, sometimes called the housing ratio, looks only at the proposed housing payment: loan principal and interest, property taxes, homeowners insurance, and any required mortgage insurance. This bundle is often called PITI. A borrower earning $6,000 a month with a $1,500 total housing payment has a 25 percent front-end ratio.

The back-end ratio adds every other monthly debt on top of the housing payment. If that same borrower also has a $300 car payment and $200 in minimum credit card payments, total monthly debt reaches $2,000 and the back-end ratio is 33.3 percent. Most underwriting focuses on the back-end number because it shows the full monthly picture.

Estimating Your Housing Payment

You can build your own PITI estimate before applying:

Principal and interest: run your expected loan amount and interest rate through an amortization calculator to get the monthly figure.
Property taxes: multiply the local tax rate by the home’s estimated value and divide by 12. Rates vary widely, from roughly 0.3 percent to over 2 percent of assessed value depending on where you buy.
Homeowners insurance: get a quote, or estimate using area averages. National averages run roughly $100 to $300 per month depending on location, coverage, and the home itself.
Mortgage insurance: if your down payment on a conventional loan is under 20 percent, expect private mortgage insurance, which typically costs 0.2 to 2 percent of the loan amount annually. You can request removal once the loan balance falls to 80 percent of the home’s original value, and it must automatically cancel at 78 percent. FHA loans carry an upfront premium plus an annual premium generally between 0.45 and 1.05 percent of the loan.⁸

Add the four components, divide by gross monthly income for the front-end ratio, then add your other monthly debts and divide again for the back-end ratio.

What DTI Do You Need to Qualify

There is no single cap that applies to every mortgage. The limit depends on the loan program, how the file is underwritten, and whether you have offsetting strengths. The federal Qualified Mortgage rule once imposed a hard 43 percent back-end DTI cap, but that limit was replaced in 2021 with a price-based standard, so exceeding 43 percent no longer automatically disqualifies a General QM loan.⁹

Conventional Loans

For conventional loans run through Fannie Mae’s Desktop Underwriter, the maximum DTI is 50 percent. Manually underwritten conventional loans are generally capped at 45 percent.¹⁰ Automated underwriting weighs several factors at once (credit score, reserves, down payment, loan-to-value), so a borrower with strong credit and real savings may clear a higher DTI than one without those cushions.

FHA Loans

FHA uses a two-tier guideline: 31 percent on the front end and 43 percent on the back end. With compensating factors such as strong cash reserves, a solid credit history, or a minimal increase in housing costs, borrowers may qualify with a back-end DTI as high as 50 percent. The number of compensating factors dictates how far above 43 percent a lender will go. And keep the FHA student loan rule in mind: the 0.5-percent-of-balance calculation can push your ratio higher under FHA than it would be conventionally.⁷

VA Loans

The Department of Veterans Affairs sets a baseline maximum DTI of 41 percent. Borrowers above 41 percent can still qualify by meeting the VA’s residual income requirement, the amount left over each month after paying major obligations.¹¹ When DTI exceeds 41 percent, residual income must exceed the guideline for your region and family size by at least 20 percent.⁴

Applying with a Co-Borrower

When two or more people apply together, the lender combines everyone’s income and everyone’s debts into a single DTI. That helps when a co-borrower brings strong income and little debt, and hurts when they bring the reverse.¹⁰

How to Lower Your DTI Before Applying

If your number is too high, you have two levers: cut monthly debt payments or raise gross monthly income. The most useful moves:

Pay down revolving debt first. Credit card balances drive minimum payments directly, and paying a card to zero removes that payment from the ratio entirely.
Pay off small installment loans. If a car loan or personal loan has only a few months left, retiring it wipes the full monthly obligation out of your DTI.
Don’t open new accounts. New credit cards or loans in the months before you apply add to your monthly obligations.
Increase your income. A raise, a better-paying job, or documented side income shifts the ratio, though lenders need a track record before freelance or gig earnings count.
Lower the loan amount. A larger down payment shrinks the mortgage payment inside your DTI. Just don’t drain savings the lender may want to see as reserves.

Focus on whichever move produces the largest drop in monthly payments for the effort involved. Eliminating a $400 car payment does more for your DTI than adding $400 in gross monthly income, because the income figure is pre-tax while the debt figure is the full payment.

1
Office of the Law Revision Counsel. 15 USC 1639c – Minimum Standards for Residential Mortgage Loans
2
Fannie Mae. B3-6-05, Monthly Debt Obligations
3
eCFR. 12 CFR 1026.43 – Minimum Standards for Transactions Secured by a Dwelling
4
eCFR. 38 CFR 36.4340 – Underwriting Standards, Processing Procedures, Lender Responsibility, and Lender Certification
5
Fannie Mae. Underwriting Factors and Documentation for a Self-Employed Borrower
6
Fannie Mae. Rental Income
7
U.S. Department of Housing and Urban Development. Mortgagee Letter 2021-13
8
Consumer Financial Protection Bureau. When Can I Remove Private Mortgage Insurance (PMI) from My Loan?
9
Consumer Financial Protection Bureau. Qualified Mortgage Definition Under the Truth in Lending Act (Regulation Z): General QM Loan Definition
10
Fannie Mae. Debt-to-Income Ratios
11
FDIC. VA Home Purchase Loan Program