Operating Expense Ratio (OER)

Written By
Paul Tracy
Updated September 30, 2020

What is the Operating Expense Ratio (OER)?

The operating expense ratio (OER) is equal to a company's operating expenses divided by its revenues. The measure is very common in real estate analysis, whereby analysts are measuring the costs to operate a piece of property versus the income it generates. 

Operating Expense Ratio (OER) Formula

OER = Operating Expenses / Revenues

Let's assume Company XYZ's operating expenses in 2019 were $2,000,000 and its revenues were $10,000,000. Using the formula above, we can calculate that Company XYZ's OER is:

OER = $2,000,000 / $10,000,000 = 20%

If Company XYZ were a real estate company, it might calculate the OER on a potential property similarly. Let's assume it could rent a property to tenants for $100,000 a month but would have to pay $35,000 a month in utilities, maintenance, insurance, and upkeep. In that case:

OER = $35,000 / $100,000 = 35% per month

Why the Operating Expense Ratio Matters

Operating expenses are costs associated with running a business's core operations on a daily basis. Thus, the lower a company's operating expenses are, the more profitable it generally is. Over time, changes in the OER indicate whether the company can increase sales without increasing operating expenses proportionately (i.e., if the business is scalable). In real estate, companies can compare properties by using the ratio.

As such, the OER is also a measure of managerial flexibility and competency that makes companies easier to compare. However, it is important to note that some industries have higher OERs than others. This is why comparing OERs is generally most meaningful among companies within the same industry, and the definition of "high" or "low" expenses should be made within this context.