Summary: Lenders compute DSCR as net operating income divided by total annual debt service (PITIA). The critical detail: most lenders use market rent from the appraisal's rent schedule, apply a 5 to 10 percent vacancy factor, and load operating expenses, which usually produces a lower ratio than the investor's spreadsheet. Worked example: $2,400 rent, 5% vacancy, $700 monthly expenses, $2,000 PITIA gives a 1.20 DSCR.
The DSCR formula fits on an index card. The lender's application of it does not. This guide walks through the exact calculation lenders perform, flags every conservative adjustment they make to your numbers, and works a complete example so you can underwrite deals the way the underwriter will.
DSCR equals net operating income divided by total annual debt service. Net operating income is effective gross income (gross rent minus vacancy and collection loss) minus operating expenses: property taxes, insurance, maintenance, property management, HOA dues, and utilities the owner pays. It excludes the mortgage payment, depreciation, and income taxes. Debt service is the full annual PITIA: principal, interest, taxes, insurance, and association dues.
Note the subtlety: property taxes and insurance appear on both sides of the ledger conceptually, but in the formula they sit inside operating expenses on the income side and inside PITIA on the debt side. Do not double-count them, and do not omit them from either side.
Four adjustments separate your spreadsheet from the underwriter's. First, market rent: the appraiser's rent schedule (Form 1007) sets the income, and if market rent is below your lease or pro forma, the lower number wins. Second, vacancy: lenders apply 5 to 10 percent even on fully occupied properties, and more in soft markets. Third, management: many lenders load a management fee of 8 to 10 percent of rent into expenses whether you self-manage or not. Fourth, short-term rental income gets haircut: lenders typically use 75 percent of Airbnb income or the long-term market rent, whichever is lower.
Take a single-family rental: gross rent $2,400 per month, 5 percent vacancy, $700 per month in operating expenses, and $2,000 per month PITIA. Effective gross income is $2,400 times 12 times 0.95, or $27,360. Subtract operating expenses of $8,400 and net operating income is $18,960. Annual debt service is $24,000. DSCR equals $18,960 divided by $24,000, or 0.79.
That 0.79 surprises investors who eyeballed the deal as cash-flowing: $2,400 rent against a $2,000 payment looks positive until vacancy and expenses enter. To reach 1.0 on the same payment, the property needs about $2,783 in monthly rent at 5 percent vacancy; to reach 1.25, about $3,158. This is why underwriting to the lender's math before offering is non-negotiable.
Commercial lenders often use debt yield alongside or instead of DSCR. Debt yield equals NOI divided by the loan amount, and it measures the lender's return if they had to foreclose and operate the property. A 1.25 DSCR on a 7 percent loan implies roughly an 8.75 percent debt yield. Debt yield has an advantage over DSCR: it is immune to interest-rate manipulation, because it ignores the rate entirely. When rates are volatile, lenders lean on debt yield to keep underwriting honest.
For residential DSCR borrowers the practical point is simpler: if a lender quotes you a debt yield requirement instead of a DSCR minimum, convert it. Divide the debt yield by your interest rate to get the implied DSCR. A 9 percent debt yield requirement at 7 percent interest is a 1.29 DSCR requirement in disguise.
Investors routinely miscalculate DSCR in four ways: using gross rent instead of effective rent after vacancy, forgetting to include property taxes and insurance in operating expenses, annualizing a best-month rent instead of a realistic average, and excluding HOA dues or management fees they plan to 'handle themselves.' Each mistake inflates the ratio, and lenders correct all four, which is why borrower-computed DSCRs almost always exceed lender-computed ones. Compute it the lender's way first and there are no surprises.
DSCR = net operating income / total annual debt service (PITIA). NOI is effective rental income minus operating expenses, excluding the mortgage payment.
Most use market rent from the appraisal's rent schedule (Form 1007), especially when it differs from your lease or pro forma. Conservative underwriting also applies vacancy factors and management fees.
Typically 5 to 10 percent, applied even to fully occupied properties. Soft markets and short-term rentals get higher vacancy loadings.
Lenders typically use 75 percent of documented Airbnb income or the long-term market rent, whichever is lower, then apply the standard formula. Expect a conservative result.
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Figures: 2026. Sources: lender rate sheets and program guides published in 2026, Fannie Mae appraisal guidance (Form 1007 rent schedule), and commercial lending references. This page is for planning only and is not financial, tax, or legal advice. Verify with the cited source or a qualified professional.