A margin is how much of each sales dollar becomes profit — one of the clearest signals of business quality. Return on equity measures profit against what owners invested. And an economic moat (Warren Buffett’s term) is the durable advantage that lets a company keep those margins instead of having rivals compete them away.
A margin is a profit divided by revenue, shown as a percentage. Gross margin is revenue minus the direct cost of making the product — the raw profitability of what’s sold. Operating margin is what’s left after the day-to-day costs of running the business (salaries, marketing, rent), before interest and tax. Net profit margin is the bottom line: profit after everything, i.e. the share of each sales dollar that actually reaches shareholders.
Example (illustrative): a company sells $100 of product that costs $65 to make, so gross profit is $35 and gross margin is 35%. If running the business costs another $20, operating profit is $15 (15% operating margin). After interest and tax take a further $5, net profit is $10 — a 10% net margin, ten cents of every sales dollar kept. A rival with the same $100 in sales but a 3% net margin keeps just three cents. Illustrative arithmetic, not a real company or a recommendation.
Margins measure profit against sales; return on equity (ROE) measures profit against the money shareholders have invested. A consistently high ROE — say a return on equity of 18% held steady for years — signals a company that turns owners’ capital into profit efficiently. Margins and ROE together separate a genuinely high-quality business from one that is merely large.
Fat margins attract competitors, who cut prices and compete profits away — unless something protects the business. Warren Buffett popularised the term economic moat for that protection: a durable competitive advantage, the way a moat protects a castle. Common moats are a powerful brand, network effects, high switching costs, patents, or an unbeatable cost advantage. A wide moat is what lets a company sustain high margins and ROE for years — which is what makes it worth a premium. Great margins with no moat are fragile. (“Economic moat” and “competitive advantage” don’t yet have their own Quantustik glossary pages — they’re explained here.)
General investor education, not personalized advice. The margin figures ($100 revenue, $65 cost → a 35% gross margin, etc.) are illustrative arithmetic, not a real company or a recommendation. The economic-moat idea is attributed to Warren Buffett, not folk wisdom. High margins without a moat are fragile — unprotected profits attract competition.
They’re profit at three points down the income statement, each divided by revenue. Gross margin is after the direct cost of making the product; operating margin is after the day-to-day costs of running the business; net margin is after everything, including interest and tax — the share of each sales dollar that reaches shareholders.
A term Warren Buffett popularised for a durable competitive advantage that protects a company’s profits, like a moat protects a castle. Examples: a strong brand, network effects, high switching costs, patents, or an unbeatable cost advantage. A wide moat lets a company keep high margins for years instead of having rivals compete them away.
Because unusually high profits attract competitors, who cut prices and chase those profits until they shrink — unless the company has a moat to keep them out. That’s why a business with great margins but no durable advantage is fragile: the profits are real today but may not last.
Investor education only — not investment advice, and never a promise of profit. Every investment can lose value.