To calculate DSCR in real estate, divide the property’s net operating income by its annual debt service: NOI ÷ annual mortgage payments (principal and interest combined). A result above 1.0 means the property earns more than it owes each year; a result below 1.0 means it doesn’t. If a fourplex produces $120,000 in NOI and the annual mortgage totals $100,000, the DSCR is 1.20, meaning $1.20 of income backs every $1.00 of debt.
That single number drives most investment property lending decisions, so getting the inputs right matters more than the arithmetic.
Step One: Calculate Net Operating Income
NOI is where the calculation usually breaks. Start with gross rental income from every unit. Add any ancillary income the property generates: laundry machines, parking, storage rentals. From that total, subtract operating expenses:
- Property taxes
- Insurance premiums
- Property management fees
- Maintenance and repairs
- Utilities the landlord pays
- Other recurring operating costs
Now the exclusions, which trip people up constantly. Do not subtract mortgage payments, depreciation, or capital expenditures. These are real costs of ownership, but NOI measures the property’s operating performance independent of how it’s financed and independent of how the IRS lets you write off the building over time. Put them in and your DSCR will be understated and your loan sizing will be wrong.
If you already own the property, IRS Schedule E is a useful starting point because it lists the right expense categories: taxes, insurance, management, repairs, utilities.1Internal Revenue Service. Schedule E (Form 1040) – Supplemental Income and Loss But Schedule E also treats mortgage interest and depreciation as deductible expenses, which makes sense for taxes and not for DSCR.2Internal Revenue Service. 2025 Instructions for Schedule E (Form 1040) (2025) Add both back when you convert the tax return into a clean NOI figure.
For a property you’re buying, gross rental income comes from current lease agreements, certified rent rolls, or the listing’s historical operating statements. Lenders read these carefully. Fannie Mae, for example, flags electronically signed leases that arrive without corroborating evidence like payment receipts or security deposit records.3Fannie Mae. Best Practices for Rental Income Verifications
Step Two: Calculate Annual Debt Service
Annual debt service is the total of the year’s mortgage payments, principal and interest combined. Take the monthly payment and multiply by twelve. Before closing, pull the payment figure from the lender’s loan estimate or term sheet rather than a rough online calculator.
A few loan structures require care:
Adjustable-rate loans. Payments change after the fixed period ends, and lenders often underwrite using the higher projected payment rather than the current one.
Balloon loans. The annual debt service during the term may look manageable while a large lump sum sits at maturity. The DSCR will look healthier than the exit picture.
Interest-only loans. This is the biggest trap. An interest-only monthly payment is lower than the amortizing payment, which automatically inflates the DSCR. Fannie Mae’s multifamily guide requires underwriters to calculate DSCR using the fully amortizing payment regardless of whether the loan has an interest-only period.4Fannie Mae Multifamily Guide. Underwritten DSCR Many private DSCR lenders do the same. If a lender allows the interest-only payment in the ratio, the paper number looks better, but the property still has to support the amortizing payment eventually.
Reading the Result
A DSCR of 1.0 means the property breaks exactly even. Every dollar of income is spoken for by the mortgage, with nothing left for a bad month. Below 1.0, the property loses money and you cover the shortfall from other sources. Above 1.0, there’s a cushion.
Lenders generally read the scale like this:
- Below 1.0: negative cash flow. Most lenders decline, or they require a much larger down payment to shrink the loan and lift the ratio.
- 1.0 to 1.19: thin margin. Some lenders will fund in this band, but expect higher rates and tighter terms. A single vacancy or repair can push the property negative.
- 1.20 to 1.50: the common approval band for investment property loans. At 1.25, the property earns 25% more than it needs, leaving a real buffer.
- Above 1.50: strong cash flow, lower perceived risk, and typically better rates and terms.
What Number You’re Calculating Against
Minimum DSCR requirements vary by lender and program, but 1.25 is the most common threshold in institutional lending. Fannie Mae’s standard multifamily program, including DUS and small loan products, requires 1.25x for conventional properties. Its affordable housing program drops to 1.15x, and green financing sits at 1.20x. Freddie Mac’s conventional multifamily threshold is effectively 1.25x as well.5Freddie Mac. Student Housing Handout
Private DSCR lenders serving single-family and small multifamily investors can be more flexible, and some will fund at 1.0 or slightly below. The trade-off shows up in the interest rate and required down payment: the further you sit below 1.25, the more the lender tightens other terms to compensate.
DSCR and loan-to-value work together during underwriting. A stronger DSCR can offset a higher LTV, and a lower LTV can rescue a borderline DSCR. Putting more money down reduces the loan amount, lowers the annual payment, and lifts the ratio directly.
Short-Term Rentals Are Calculated Differently
If the property is a short-term rental, there’s no long-term lease to document the income side of the ratio. Most lenders substitute projected market income from third-party analytics tools like AirDNA, which use comparable properties, occupancy rates, nightly pricing, and seasonality to estimate annual revenue. If the property has 12 to 24 months of booking platform history, that actual data carries more weight than projections.
Some lenders skip short-term rental income altogether and underwrite using a market rent analysis, essentially treating the property as a long-term rental. That produces a more conservative DSCR and typically means a larger down payment if the long-term numbers are weaker.
Running the Formula Backward
The same equation sizes an offer before you make one. Start with the lender’s minimum DSCR and the property’s realistic NOI, then solve for the maximum annual debt service the property can support:
Maximum annual debt service = NOI ÷ minimum DSCR
That figure translates directly into a maximum loan amount at a given rate and term, which then tells you how much you can offer and how much you’ll need to put down. If the ratio still doesn’t clear the threshold, the levers are the same two variables in the formula. On the income side: raise rents toward market, reduce vacancy, cut operating expenses. On the debt side: a larger down payment, discount points to buy the rate down, or a longer amortization (30 years instead of 25) to lower the annual payment. A longer amortization improves the ratio but increases total interest paid over the life of the loan.