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What is the Operating Expense Ratio (OER)?

Understanding the Operating Expense Ratio (OER)

The Operating Expense Ratio or OER, is one of the vital metrics used by investors to assess the efficiency of a company’s operations. For a novice investor, it might seem overwhelming initially, but understanding and interpreting the operating expense ratio is a considerable step towards becoming market-savvy and making informed investment decisions.

Defining the Operating Expense Ratio (OER)

The Operating Expense Ratio (OER) is used to measure a company’s operational efficiency. It is a financial metric that compares a company’s operating expenses to its net sales. The OER is often expressed as a percentage. It quantifies the proportion of a company’s income that is spent on cost of goods sold (COGS) and other operating expenses such as wages and rent, before interest and taxes. Essentially, the OER indicates how much money is taken out of revenues to maintain operations.

Formula of Operating Expense Ratio (OER)

In simple terms, the Operating Expense Ratio is calculated by dividing the Operating Expenses by the net Operating Income.

OER = Operating Expenses / Net Operating Income

Breaking down the Operating Expense Ratio

Operating Expenses: comprise the costs associated with the day-to-day operations of a company. These might include rent or mortgage payments, utilities, leasing expenses, salaries, and other regular operational costs.

Net Operating Income: Net operating income is the amount of money that an entity makes after deducting the cost of the goods sold but before taking into account interest and taxes.

However, it’s crucial to note that the Operating Expense Ratio is industry-dependent and can greatly vary from one business sector to another.

Interpreting the Operating Expense Ratio (OER)

The OER is a gauge of operational efficiency and financial health. A lower OER typically indicates higher operational efficiency, while a higher OER suggests lower efficiency. Generally, a lower percentage implies the company is earning more while spending less to generate that profit and therefore stands in a comparatively better position financially.

In principle, an increase in the OER over time might infer that the company’s management is failing to control costs, which could affect profitability. Comparatively, a decrease in the OER signifies that the company is becoming more efficient at generating income.

However, while the OER is a valuable tool, it should not be used in isolation for investment decisions. Understanding the context, industry norms, and the specific nature of the company’s expenses are equally crucial.

How the Operating Expense Ratio (OER) benefits investors

Investors use the OER as one of several tools to analyze a company’s performance, gaining insight into its cost management and operational efficiency. It is used in conjunction with other financial ratios to paint a comprehensive picture of a company’s financial health.

Companies with a lower OER are likely better at managing their costs, subsequently generating larger profits. Conversely, a higher OER means higher business operating costs regarding the company’s income, possibly leading to lower profitability.

Limitations of the Operating Expense Ratio (OER)

While the OER is a useful metric, it isn’t without its limitations. The OER does not account for capital structure considerations or financial expenses, for instance, interest expenses or costs related to debt servicing. It also excludes non-operating expenses and one-off payments, often leading to an incomplete or skewed understanding of a company’s total cost profile.

Consequently, while it’s advisable to incorporate the OER in investment decision-making, it should only make up one part of an investor’s overall evaluation strategy.


Understanding the Operating Expense Ratio is a fundamental part of financial literacy for novice and seasoned investors alike. By comparing a company’s operating expenses to its net sales, the OER provides insight into a company’s efficiency at managing costs and generating profit. However, it should not be used as the sole determining factor in investment decisions. Instead, it should supplement other analysis tools, accounting for industry standards and broader economic conditions, to yield a comprehensive understanding of a company’s financial health.