Operating Expense Ratio

Operating expense ratio (OER) is a property's operating expenses divided by its gross operating income, expressed as a percentage. It measures how much of each revenue dollar is consumed by the cost of running the property. A lower OER means more income survives to net operating income, so OER is a quick read on operating efficiency.

How Is Operating Expense Ratio Calculated?

Operating expense ratio is calculated by dividing total operating expenses by gross operating income, then multiplying by 100. The formula is OER = (Operating Expenses / Gross Operating Income) x 100. Per Commercial Real Estate Loans, a property with $40,000 of operating expenses and $100,000 of gross income has a 40% OER.

The ratio depends on what counts as an operating expense. Per Commercial Real Estate Loans and Adventures in CRE, operating expenses include property taxes, insurance, utilities, repairs and maintenance, and management fees. They exclude debt service and capital expenditures, which are financing and long-term investment items, not the recurring cost of operations.

Because capital expenditures and debt service are excluded, OER isolates the cost of operating the asset from how it is financed or improved. Including them inflates the ratio and misstates efficiency.

Why Operating Expense Ratio Matters

Operating expense ratio matters because it is a fast diagnostic on whether a property is run efficiently or leaking money. A rising OER over time means expenses are growing faster than income, which compresses NOI and, through the cap rate, value. Two similar buildings with different OERs tell an underwriter which one has an expense problem.

The ratio is also a screen for misrepresentation. Per HelloData, a good multifamily OER typically falls between 35% and 50%. An OER far below that range can signal deferred maintenance or omitted expenses such as a management fee, not genuine efficiency, while an OER far above it signals older systems or operational slack. Either extreme is a prompt to examine the operating statement line by line.

This is why OER is compared against property type and vintage, not judged in isolation. A 40% OER is healthy for gross-leased multifamily and alarming for a triple-net single-tenant asset. Context is the difference between a useful ratio and a misleading one.

Example

A multifamily property collects $850,000 in gross operating income for the year and incurs the operating expenses shown below, spanning property taxes, insurance, utilities, repairs and maintenance, and a management fee. The table lists each expense line, totals them into a single figure, and derives the operating expense ratio from that total against gross operating income.

Operating expense ratio is $277,000 / $850,000 = 32.6%. That sits just below the 35% to 50% multifamily range HelloData cites, which is a prompt to confirm no expense is missing rather than to assume standout efficiency. Note that if a $150,000 roof replacement were incorrectly counted as an operating expense, OER would jump to 50.2%, distorting the read.

Variations and Edge Cases

Operating expense ratio varies widely by property type and lease structure, so a benchmark from one asset class misleads in another. The driver is who pays the expenses. In triple-net structures, tenants pay most operating costs directly, so the owner's OER is low; in full-service gross leases, the owner absorbs the costs, so OER is high.

These are representative ranges, not fixed thresholds. The recurring error is comparing a gross-leased property's OER against a net-leased benchmark, which makes a normal building look inefficient or a stripped statement look exceptional.

Operating Expense Ratio vs Operating Expenses

Operating expense ratio is often confused with operating expenses, but one is a rate and the other is a dollar total. Operating expenses are the sum of the costs to run a property, a currency figure. Operating expense ratio is that figure divided by gross operating income, a percentage that shows what share of revenue the expenses consume.

The difference is amount versus proportion. Two properties can have identical operating expenses of $300,000, but if one earns $600,000 and the other $1,000,000 in gross income, their OERs are 50% and 30%. OER normalizes for size, which is why it is used to compare efficiency across properties.

Frequently Asked Questions

What is the formula for operating expense ratio?Operating expense ratio equals total operating expenses divided by gross operating income, multiplied by 100. Operating expenses include taxes, insurance, utilities, repairs, and management, but exclude debt service and capital expenditures.

What is a good operating expense ratio for multifamily?A good multifamily operating expense ratio typically falls between 35% and 50%, per HelloData. Below 35% can indicate high efficiency or omitted expenses; above 50% often signals older systems or operational slack. Compare against property type and vintage.

Does operating expense ratio include the mortgage?No. Operating expense ratio excludes debt service and capital expenditures. It measures the recurring cost of operating the property, not how it is financed, so it isolates operational efficiency from the loan structure.

Related Terms

• Operating Expenses

• Net Operating Income

• Effective Gross Income

• Operating Statement

• Cap Rate