Debt Service Coverage Ratio is the primary metric lenders use to size commercial real estate loans. It is defined as net operating income divided by annual debt service, the total principal and interest payments required on the proposed loan over twelve months.
A DSCR above 1.0 means the property generates more income than its debt costs; below 1.0 the property cannot service its own debt from operations alone. Most institutional lenders require a minimum DSCR of 1.20x to 1.30x on stabilized permanent loans, meaning NOI must exceed annual debt service by at least 20-30%.
This cushion protects the lender against moderate income shortfalls and gives the borrower room to operate through vacancy spikes, capex timing, or market softness without triggering a default.
Loan sizing is the practical output of DSCR underwriting. A lender works backward from the property's underwritten NOI: divide NOI by the required minimum DSCR to derive the maximum supportable annual debt service, then apply that debt service figure to the proposed loan's amortization schedule and interest rate (expressed as the mortgage constant) to determine the maximum loan balance.
For a property generating $600,000 in NOI with a 1.25x DSCR requirement and a mortgage constant of approximately 8.1% (6.5% interest, 25-year amortization), maximum supportable debt service is $480,000 and the maximum loan is roughly $5.9 million. This calculation runs alongside a loan-to-value test; whichever constraint (DSCR or LTV) produces the lower loan amount governs the underwrite.
Stress testing extends DSCR analysis beyond the stabilized base case. Lenders apply scenarios assuming 10-20% rent declines from underwritten levels, vacancy increases of 300-500 basis points, or rising interest rates on floating-rate structures to assess how debt coverage holds under adverse conditions.
Bridge lenders and construction lenders evaluate DSCR on a projected exit basis, because the property does not yet generate stabilized income during the loan term; coverage is modeled at the anticipated refinancing or sale. Some lenders supplement DSCR with a debt yield test (NOI divided directly by loan amount, bypassing cap rate inputs entirely) which provides a cap-rate-agnostic view of coverage particularly useful when cap rates are historically compressed and DSCR metrics can appear adequate while debt yield signals overleveraging.
DSCR interacts with lease rollover risk and interest rate exposure in ways that require integrated analysis. A property with solid current coverage may face material downside if a major tenant's lease expires within the loan term; lenders model rollover scenarios by applying market re-leasing assumptions and downtime to the projected income stream, then recalculating coverage at the stressed rent and occupancy.
Floating-rate loans add rate sensitivity: a 1.35x DSCR at origination can fall below 1.0x if benchmark rates rise sharply, as happened broadly during the 2022-2024 rate cycle and contributed to distress across office and value-add multifamily portfolios underwritten at near-zero base rates. For borrowers, understanding DSCR not as a compliance threshold but as a framework for modeling debt capacity across scenarios is foundational to disciplined capital structure decisions in commercial real estate.