GLOSSARY

What Is the Multifamily Operating Expense Ratio?

Learn the multifamily operating expense ratio formula, see a worked example, and understand why a lower ratio is not always a better operating result.

The multifamily operating expense ratio, or OER, shows how much of a property's effective gross income is used to cover operating expenses. It is a cost-efficiency measure, not a complete measure of investment return.

Operating expense ratio = operating expenses ÷ effective gross income × 100

Fannie Mae expresses OER as a percentage of effective gross income in its multifamily operating-statement definitions. Use a consistent accounting policy for the costs and income included.

A quick example

A fictional apartment property has annual operating expenses of USD 900,000 and effective gross income of USD 2,000,000.

Its OER is 45%: 900,000 divided by 2,000,000, multiplied by 100. Under the same income and expense definitions, NOI is USD 1,100,000.

These figures illustrate the calculation. They are not a recommended expense ratio or a Leni customer result.

What does a rising ratio mean?

A rising ratio can reflect higher costs, weaker income, or both. Expenses could stay flat while concessions reduce income, causing OER to rise without any new spending.

Look at the numerator and denominator separately. Then review expenses per unit, account-level movements, and the reporting period.

A lower ratio is not automatically better. Missing accruals or deferred maintenance can make the current figure look attractive while hiding a problem.

How should we compare properties?

Use the same expense scope, income definition, period, and accounting basis. Compare assets with similar characteristics, and keep unusual items visible.

Do not compare one property's monthly result with another's trailing-year result. Do not treat a difference caused by account mapping as an operating improvement.

Is OER the same as cash flow?

No. OER compares operating expenses with effective gross income. Cash flow also depends on items outside that relationship, such as financing and capital spending. Review the complete report before making a decision.

How can Leni help us review the ratio?

With the relevant authorized sources available, we can support analysis of the income and expense movements behind a ratio. Our Universal Data Model helps organize supported source data using consistent definitions.

Ask: “Show the income and expense changes behind this property's OER movement, and flag any differences in the periods or account mappings.”

For the broader income relationship, see what NOI means.