Definition
Operating expense ratio measures operating expenses as a percentage of revenue.
Formula
Operating expense ratio = operating expenses / revenue
Example
Opex $600k on $2M revenue yields a 30% ratio.
How to use it
- Track by function to see which teams scale with revenue.
- Use trailing periods to smooth volatile months.
Common mistakes
- Comparing ratios without adjusting for revenue recognition timing.
- Treating one-time expenses as recurring operating cost.
Why this matters
This term matters because cash timing and risk are usually the difference between a plan that works on paper and a plan that survives. Use consistent definitions so decisions are comparable over time.
Practical checklist
- Write a 1-line definition for "Operating Expense Ratio" that your team will use consistently.
- Keep the time window consistent (weekly/monthly/quarterly) when comparing trends.
- Segment results (channel/plan/cohort) before drawing big conclusions from blended averages.
- Sanity-check with a related calculator from the same category on MetricKit.
- Document common pitfalls so the metric doesn't get gamed.
Where to use this on MetricKit
Calculators
- Profitability Index Calculator: Calculate profitability index (PI) from discounted cash flows and estimate the max investment for a target PI.
- WACC Calculator: Calculate WACC (Weighted Average Cost of Capital) from capital structure, cost of equity, cost of debt, and tax rate.
- Equity Value Calculator: Convert enterprise value (EV) into equity value using cash, debt, and other adjustments (optionally per share).
- Pre-money vs Post-money Valuation Calculator: Convert between pre-money and post-money valuation and estimate investor ownership from a financing round size.
- Pro Rata Investment Calculator: Estimate how much you need to invest in a new round to maintain your ownership percentage (simplified).
Guides
- WACC explained: how to estimate a discount rate for DCF: A practical guide to WACC: what it is, how to compute it, and how to use it (carefully) as a DCF discount rate.
- Discount rate: how to choose it for NPV and DCF: A practical guide to discount rates: what they mean, how to choose a rate (WACC vs MARR), and how to avoid common mistakes.
- Enterprise value vs equity value: how to bridge EV to equity: A practical guide to converting enterprise value (EV) into equity value using net debt and other claims (and avoiding common valuation mix-ups).
- Pre-money vs post-money valuation: formulas, ownership, and pitfalls: Learn pre-money vs post-money valuation, how investor ownership is estimated, and why the option pool shuffle changes effective dilution.
- Pro rata rights: what they mean and how to estimate your check size: A practical guide to pro rata rights: maintaining ownership, estimating dilution if you don't participate, and common allocation pitfalls.