By Brandon Sooknanan, Founder of StatementReady
Once a broker has a monthly income figure for a self-employed borrower, the next question on the file is the debt-to-income ratio. On a bank statement loan, that income figure comes from a worksheet built off 12 or 24 months of deposits rather than from W-2s, but the DTI arithmetic itself is the same. This post walks through that arithmetic and where the inputs come from, so the number you carry into your review is one you can explain.
What DTI is
The CFPB puts it plainly: "Your debt-to-income ratio (DTI) is all your monthly debt payments divided by your gross monthly income." It adds that "Different loan products and lenders will have different DTI limits." (CFPB, "What is a debt-to-income ratio?", fetched Nov 4, 2026.)
Fannie Mae's Selling Guide describes the ratio as having "two components": total monthly obligations, and the borrower's stable monthly income (Selling Guide B3-6-02, Debt-to-Income Ratios, fetched Nov 4, 2026). Non-QM bank statement programs set their own rules, so treat any agency page as background and the lender's matrix as the rule for your file.
Front-end vs back-end
Two ratios come up on the file:
- Front-end DTI (housing only) = proposed monthly housing payment ÷ gross monthly income
- Back-end DTI (housing + other debts) = (proposed monthly housing payment + other monthly debts) ÷ gross monthly income
A quick example with round numbers: gross monthly income of $10,000, a proposed housing payment of $2,800, and other monthly debts of $900 (an auto payment and two card minimums).
- Front-end: 2,800 ÷ 10,000 = 28.00%
- Back-end: (2,800 + 900) ÷ 10,000 = 37.00%
Whether either number works depends entirely on the lender and program. The math doesn't tell you that; the lender's guidelines do.
Where the inputs come from on a bank statement file
Gross monthly income. On a bank statement loan this is the figure from the income worksheet: eligible deposits over the look-back period, after whatever expense factor or ownership percentage the lender applies, divided by the number of months. Expense factors and look-back periods vary by lender and program, so build the worksheet to the lender you're submitting to before you run DTI. If the income figure is wrong, both ratios are wrong.
Proposed housing payment. Use the full monthly housing payment you're using for the file: principal and interest plus whatever escrows and dues the lender counts. Check the lender's list so you aren't leaving out an HOA due or flood premium.
Other monthly debts. Pull these from the credit report and the application, then confirm with the lender which debts count, which can be excluded and with what documentation. Business debts paid from business accounts come up on self-employed files; ask the lender rather than assuming.
Common slips worth checking
- Mixing gross and net. DTI uses gross monthly income. On a bank statement worksheet, make sure you're using the income figure the lender's method produces, not raw deposits.
- Stale income. If you rebuilt the worksheet after removing a large deposit, re-run DTI with the new figure.
- Missing debts. A new account that shows on an updated credit report changes back-end DTI.
- Rounding. Small rounding differences near a lender's limit matter. Keep two decimals and note the formula you used.
A free calculator that shows its work
We built a free mortgage DTI calculator for this step. You enter gross monthly income (including a bank statement income figure), the proposed housing payment and each other monthly debt, and it shows front-end and back-end DTI, rounded to two decimals, with the formula printed on the page.
A few things it deliberately doesn't do:
- It sets no limit. There's no pass/fail color and no "approved" message. Limits vary by lender and loan program, so confirm the limit with the lender.
- It doesn't send anything. It runs in your browser, and what you type isn't sent or stored.
- It doesn't need an account.
If you need the income figure first, the free bank statement income calculator gives a 12- or 24-month view from monthly deposit totals, and you can carry its monthly figure into the DTI field.
Where DTI fits in the review
DTI is one input to the broker's review of the loan file, not a decision. The lender's underwriting decides approval. What a clean DTI calculation does give you is a number you can show your work on: the income figure and where it came from, the housing payment and its parts, and each debt you counted. That makes the conversation with the lender's scenario desk faster when something is close.
When you're ready to work from the real statements, StatementReady builds the bank statement income worksheet from uploaded PDFs and checks whether each statement's transactions add up to its printed balances. It assists your review; the lender makes all underwriting decisions.
Not legal or tax advice. StatementReady isn't affiliated with or endorsed by Fannie Mae, the CFPB or any lender.
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