Operating Margin
Operating margin is operating income divided by revenue. It shows what percentage of each dollar of sales the core business keeps after paying the costs of running it: production, salaries, marketing, research, but before interest and taxes.
The math
2 billion dollars of revenue, 400 million of operating income: a 20 percent margin. The power is in small moves.
If that margin slips to 17 percent, profit drops by 60 million, a 15 percent earnings hit from a 3-point margin change. Multiply by the P/E the market applies and the stock can lose a quarter of its value on what looks like a minor operational slip.
| 20% margin | 17% margin | |
|---|---|---|
| Revenue | $2.0B | $2.0B |
| Operating income | $400M | $340M |
| Earnings change | -15% |
Margins are the transmission between sales and shareholder returns.
The trap
Buying peak margins in cyclical businesses. Operating margins are widest at the top of the cycle, exactly when everything looks easiest, and paying a full multiple on peak margins means overpaying twice: on the earnings level and on the multiple applied to it.
The mirror-image mistake is dismissing a good business during a temporary margin trough.
The move
Judge margin against two references only: the company’s own multi-year history and its direct competitors. A margin expanding for years signals pricing power; a margin persistently above peers signals a structural advantage worth naming before you invest.
Then confirm against free cash flow: efficiency that never shows up as cash is accounting, not economics.