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Financing · Fannie Mae B3-6-02Debt-to-income ratio limits: 36%, 45% and 50%

The debt-to-income (DTI) ratio compares the buyer's total monthly obligations – the new housing payment (principal, interest, taxes, insurance and HOA dues) plus other long-term and significant short-term debts – with the total monthly income used to qualify. On a Fannie Mae loan underwritten through Desktop Underwriter (DU), the maximum allowable DTI is 50%. For manually underwritten loans the maximum is 36% of stable monthly income, which can go up to 45% if the borrower meets the credit score and reserve requirements in Fannie Mae's Eligibility Matrix. Some transactions have lower limits, and FHA, VA and USDA loans follow their own agency's rules. A new car loan, credit card balance or co-signed debt before closing can push the ratio over the limit.

Maximum DTI (B3-6-02)

  1. DU

    50%.

  2. Manual underwriting

    36% of stable monthly income.

  3. Manual, with strengths

    Up to 45% with the credit score and reserves in the Eligibility Matrix.

  4. Lower limits

    Some cash-out refinances, borrowers without a credit score, non-occupant borrowers.

Quick example

  1. Income

    $8,000 a month

    Total monthly income used to qualify.

  2. Obligations

    $3,600

    New housing payment $2,800 + car $500 + student loan $300.

  3. DTI

    45%

    $3,600 ÷ $8,000. A new $450 car payment would bring it to 50.6%.

What the TC reminds the buyer

  • No new car, furniture on credit or new cards until after closing.
  • Do not co-sign for anyone during the transaction.
  • Tell the loan officer about any change in income or debts right away.

Questions buyers ask

What is the maximum debt-to-income ratio for a conventional loan?

For Fannie Mae loans underwritten through DU, 50%; for manually underwritten loans, 36%, or up to 45% with the required credit score and reserves (B3-6-02).

What debts count in the DTI ratio?

The new housing payment (including taxes, insurance and HOA dues) plus other long-term and significant short-term monthly debts, such as car, student and credit card payments.

Can a lender require a lower DTI?

Yes. Fannie Mae sets the maximum; individual lenders can be stricter, and government loans follow their own agency's rules.

Related guides

ClosingCode's loan update message reminds your buyer, in English or Spanish, to avoid new credit and large purchases until after closing – you review it and send it.

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Source: Fannie Mae Selling Guide B3-6-02, Debt-to-Income Ratios (04/02/2025), selling-guide.fanniemae.com, read October 25, 2026.

General information about Fannie Mae conventional loans, not legal or financial advice. Lenders often add stricter rules (overlays), and FHA, VA and USDA loans have their own. ClosingCode is software; it is not a lender. This guide is not a substitute for the advice or services of an attorney.