Debt Service Coverage Calculator Formula

Understand the math behind the debt service coverage calculator. Each variable explained with a worked example.

Formulas Used

Debt Service Coverage Ratio

dscr = net_operating_income / annual_debt_service

Annual Surplus After Debt

surplus = net_operating_income - annual_debt_service

Monthly Surplus After Debt

monthly_surplus = (net_operating_income - annual_debt_service) / 12

Variables

VariableDescriptionDefault
net_operating_incomeNet Operating Income (NOI)(USD)48000
annual_debt_serviceAnnual Debt Service(USD)36000

How It Works

Debt Service Coverage Ratio

DSCR measures the ability of a property to generate enough income to pay its debt obligations.

Formula

DSCR = Net Operating Income / Annual Debt Service

Interpretation

  • DSCR > 1.25: Strong coverage, most lenders are comfortable
  • DSCR = 1.0: Break-even, NOI exactly covers debt payments
  • DSCR < 1.0: Negative cash flow, income does not cover debt
  • Most commercial lenders require 1.20 to 1.35 minimum
  • Worked Example

    A property generates $48,000 NOI with $36,000 in annual debt payments.

    net_operating_income = 48000annual_debt_service = 36000
    1. 01DSCR = $48,000 / $36,000 = 1.33
    2. 02Annual surplus: $48,000 - $36,000 = $12,000
    3. 03Monthly surplus: $12,000 / 12 = $1,000
    4. 04A DSCR of 1.33 means the property earns 33% more than needed to cover debt

    Frequently Asked Questions

    What DSCR do lenders require?

    Most commercial lenders require a minimum DSCR of 1.20 to 1.35. Some DSCR loan programs for residential investment properties go as low as 1.0 or even 0.75 but at higher interest rates.

    What is included in annual debt service?

    Annual debt service includes all principal and interest payments on the property mortgage(s) for the year. It typically does not include operating expenses, which are already deducted to calculate NOI.

    How can I improve my DSCR?

    Increase NOI by raising rents, reducing vacancies, or cutting operating expenses. Alternatively, reduce debt service by making a larger down payment, extending the loan term, or securing a lower interest rate.

    Ready to run the numbers?

    Open Debt Service Coverage Calculator