Debt-to-Income Ratio for a Mortgage, Explained
Before a lender approves a mortgage, it wants to know whether the new payment fits alongside everything else you already owe. The main yardstick is your debt-to-income ratio, or DTI. Knowing how it is calculated lets you estimate what a lender will see before you apply, and helps you judge for yourself how much house payment your budget can carry.
1. What DTI is
The Consumer Financial Protection Bureau defines your debt-to-income ratio as all your monthly debt payments divided by your gross monthly income. Gross monthly income is generally what you earn before taxes and other deductions are taken out. The CFPB describes DTI as one way lenders measure your ability to manage the monthly payments to repay the money you plan to borrow.
2. The calculation
The CFPB's own example: a $1,500 mortgage payment, a $100 auto loan payment, and $400 a month for other debts add up to $2,000 in monthly debt payments. With a gross monthly income of $6,000, the DTI is $2,000 / $6,000, or 33%.
Here is the method as steps:
- List every required monthly debt payment: the proposed housing payment, car loans, student loans, minimum credit card payments, personal loans, and similar obligations.
- Add them up.
- Divide by your gross monthly income.
- Multiply by 100 for a percentage.
Everyday living costs like groceries, utilities, and phone bills are not debt payments, so they are not in the ratio. That is exactly why DTI is a lender's measure and not a full budget.
3. Why lenders are required to look at it
Federal rules require mortgage lenders to make a reasonable, good-faith determination that you can repay the loan. Under Regulation Z's ability-to-repay rule, a lender must consider a list of factors that includes your income or assets, employment status, the monthly payment on the loan, payments on other loans connected to the property, monthly payments for mortgage-related obligations, your current debt obligations, alimony and child support, your monthly debt-to-income ratio or residual income, and your credit history. The rule also requires lenders to verify the information they rely on, generally using reasonably reliable third-party records.
4. There is no single magic number
The CFPB is direct about this: different loan products and lenders will have different DTI limits. Rather than guess at one cutoff, it is more useful to see how the maximum housing payment changes at different levels.
Assume a gross monthly income of $7,500 and existing debts of $650 a month (a $420 car payment and a $230 student loan payment). These are illustrative figures.
| DTI level | Total debt allowed per month | Room left for the housing payment |
|---|---|---|
| 36% | $2,700 | $2,050 |
| 43% | $3,225 | $2,575 |
| 50% | $3,750 | $3,100 |
The "room left" column is the full housing payment, which typically includes principal, interest, property taxes, homeowners insurance, and any mortgage insurance or HOA dues, not just principal and interest.
5. What the table does not tell you
A lender approving you at a high DTI does not mean the payment is comfortable. DTI uses gross income, but you pay bills from take-home pay after taxes, retirement contributions, and health insurance. At 50% DTI in the example, $3,750 of the $7,500 gross is committed to debt before a single grocery trip, and take-home pay is meaningfully lower than $7,500.
A practical check is to compute the same housing payment against your actual take-home pay and your real monthly spending. If the result leaves little room for savings and irregular costs like car repairs, a lower target payment may be wiser than the maximum you can be approved for.
6. Ways to lower your DTI
- Pay down or pay off a debt with a large monthly payment. Eliminating the $420 car payment in the example adds $420 of room at any DTI level.
- Avoid new debt before applying. A new car loan or card balance raises the ratio and can change what you qualify for.
- Choose a lower-priced home or a larger down payment. Both reduce the housing payment, which is usually the biggest number in the ratio.
- Document all eligible income. Income the lender cannot verify generally cannot be counted.
7. Key takeaways
- DTI is all monthly debt payments divided by gross monthly income; the CFPB's example of $2,000 on $6,000 is 33%.
- Federal ability-to-repay rules require mortgage lenders to consider DTI or residual income, along with income, debts, and credit history.
- Limits differ by loan product and lender, so there is no single required number.
- On $7,500 gross income with $650 of other debts, the housing payment room is $2,050 at 36% and $2,575 at 43%.
- Being approved at a given DTI is not the same as being comfortable; test the payment against take-home pay too.