The Operating Expense Ratio (OER) is a financial metric that shows the percentage of revenue consumed by operating expenses. It's calculated by dividing total operating expenses by total revenue, then multiplying by 100. For angel investors evaluating startups or growth companies, OER is a straightforward lens into operational efficiency and cost management discipline.
How It Works
To calculate OER, add up all operating expenses—salaries, rent, utilities, marketing, insurance, and administrative costs—then divide by total revenue. For example, a company with $1 million in revenue and $400,000 in operating expenses has an OER of 40%. This means 40 cents of every revenue dollar goes to operations, leaving 60 cents available for gross profit, debt service, taxes, and reinvestment.
Different industries have vastly different typical OERs. Software companies often run 20-30% OER because they scale efficiently without proportional expense increases. Retail or service businesses might operate at 50-70% OER due to labor intensity and physical infrastructure costs.
Why It Matters for Investors
As an angel investor, OER tells you whether management is running a tight ship or burning cash carelessly. A declining OER over time signals improving operational leverage—the company is growing revenue faster than expenses, a hallmark of scalable businesses. Conversely, rising OER despite revenue growth suggests either operational challenges or strategic spending that isn't yet producing returns.
OER also helps you compare companies within an industry. If two competitors have similar revenue but one operates at 35% OER while the other runs 55%, the efficient operator has a structural advantage and better margins to weather downturns or invest in growth.
Example
Imagine you're evaluating a B2B SaaS startup with $2 million annual revenue. Operating expenses total $600,000 (salaries, cloud infrastructure, customer support, marketing). The OER is 30%. Compare this to a competitor with $2 million revenue but $1.2 million in operating expenses (60% OER). Your target company is operationally more efficient, likely more profitable, and better positioned for scale. This advantage might justify a higher valuation or lower funding round dilution.
Key Takeaways
- OER is a simple efficiency metric: higher revenue relative to operating expenses is generally better
- Compare OER within industries, not across them—software and retail have fundamentally different cost structures
- Declining OER over time indicates improving unit economics and operational leverage
- Use OER alongside burn rate and gross margin to build a complete picture of financial health