Real Estate Glossary
NOI Formula: How to Calculate It (With Examples)
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Definition
The NOI formula calculates a property's annual net operating income by subtracting vacancy losses and all operating expenses from gross rental income. NOI is calculated before mortgage payments, income taxes, and depreciation — making it a pure measure of property performance that is not influenced by how the property is financed.
The NOI Formula Formula
Variables explained:
Gross Rental Income = monthly rent × 12 (assuming full occupancy). Vacancy Loss = Gross Rental Income × vacancy rate (typically 5–10%). Operating Expenses = property taxes + insurance + property management fees + maintenance & repairs + utilities paid by owner + HOA fees + capital expenditure reserves. Mortgage P&I is NOT an operating expense.
NOI Formula Example
A triplex has three units renting at $1,100/month each = $3,300/month gross ($39,600/year). Vacancy allowance at 8% = $3,168. Operating expenses: property tax $6,000, insurance $2,400, management (10% of effective income) $3,643, maintenance $4,000, landscaping $600 = $16,643. NOI = $39,600 − $3,168 − $16,643 = $19,789/year.
Why NOI Formula Matters for Investors
Getting the NOI formula right is critical because errors compound through every downstream metric. Underestimating expenses is the most common mistake — particularly maintenance, capital expenditures (roof, HVAC, appliances), and vacancy. Many amateur investors use gross rent or gross rent minus just the mortgage to evaluate deals, leading to overpaying for properties.
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Frequently Asked Questions
What is included in operating expenses for NOI?
Property taxes, homeowners insurance, property management fees, maintenance and repairs, capital expenditure reserves, utilities paid by the landlord, landscaping, HOA fees, and pest control. Do not include the mortgage payment.
What is effective gross income vs. gross income in the NOI formula?
Gross income assumes 100% occupancy. Effective Gross Income (EGI) = gross income minus vacancy allowance. You then subtract operating expenses from EGI, not gross income, to get a more realistic NOI.
Should I include a CapEx reserve in my NOI calculation?
Yes. Most experienced investors include a capital expenditure (CapEx) reserve of $100–$200/month per unit to account for eventual large repairs (roof, HVAC, plumbing). Omitting it overstates NOI and understates true costs.
What is a typical operating expense ratio?
Operating expenses typically run 35–50% of gross rental income for residential rentals, and 30–45% for well-maintained single-family homes. Higher expenses reduce NOI and therefore cap rate.
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