Last updated: November 5, 2026
To calculate DSCR, divide the property's income by its debt service. For a rental, that usually means monthly gross rent divided by the full monthly payment, often principal, interest, taxes, insurance, and HOA dues. For commercial property, use annual net operating income divided by annual principal and interest.
There are two common ways people calculate DSCR, and mixing them up is the most frequent mistake. Residential investor lenders often use a simple rent-to-payment version. Commercial lenders usually use net operating income, which is income after operating expenses, against annual debt payments.
Ask the lender, or read their program guide, to learn which one applies. The math is easy once you know which inputs belong in it.
For a property already rented, the starting point is the current lease amount. For a vacant property or a purchase, lenders typically rely on a market rent estimate from the appraiser, often on a rent schedule form for one to four unit homes. Some lenders use the lower of the lease and the market estimate.
For the commercial version, start from gross income, subtract vacancy and operating costs like management, repairs, utilities the owner pays, taxes, and insurance. What remains is net operating income.
For the residential version, add up the full proposed housing payment: principal and interest on the new loan, monthly property tax, monthly insurance, and any association dues. Some people call this PITIA.
For the commercial version, use annual principal and interest only, because taxes and insurance were already removed when you calculated net operating income.
Divide income by debt service. Here is a worked example using made-up round numbers for illustration only. Suppose a rental brings in 2,400 per month in rent. The proposed payment including taxes, insurance, and dues is 2,000 per month. 2,400 divided by 2,000 equals 1.20.
A result of 1.20 means the rent covers the payment with 20 percent to spare. A result of 0.90 would mean the rent covers only 90 percent of the payment, so the owner would cover the shortfall out of pocket.
For a duplex, triplex, or fourplex, add the rent from every unit to get the income figure. The payment stays a single number for the whole loan. If one unit is owner-occupied, the property usually no longer fits a DSCR investor program, so check with the lender before you run numbers that assume it does.
The two levers are income and payment. You can raise income with a stronger lease or a property that rents better. You can lower the payment with a larger down payment, a lower rate, a longer amortization, or an interest-only period if a lender offers one. Each choice has tradeoffs worth discussing with a licensed lender.
Is DSCR calculated monthly or annually? Either works as long as both numbers use the same period.
Does vacancy factor in? In many residential programs, no. In commercial underwriting, usually yes.
Where can I learn the formula in more depth? See briefcase.email/guides/dscr-formula and the full overview at briefcase.email/guides/dscr-loans.
Educational note: This page is general information for learning purposes, not lending, tax, or legal advice. Briefcase is a media and marketing company, not a lender or broker, and does not originate loans. Loan terms, ratios, and eligibility vary by lender and by deal, so confirm every figure with a licensed lender before you act.
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