Costs, Margins, and Profitability
How a dollar of revenue turns into a few cents of profit, the three margins investors use to measure it, and why some companies' profits swing much more than their sales.
The short version
Revenue passes through several layers of cost before it becomes profit: the direct cost of what was sold, operating expenses like research and marketing, then interest and taxes. Margins express each layer of profit as a share of revenue, which makes companies of different sizes comparable. Gross margin, operating margin, and net margin each tell you something different. Because some costs are fixed, profit can rise and fall faster than sales, a pattern called operating leverage. Margins vary hugely by industry, so compare within an industry and over time.
By the end of this lesson, you'll be able to
- Follow revenue down to net income through each layer of cost
- Calculate gross, operating, and net margins
- Explain fixed and variable costs and how operating leverage magnifies changes in sales
Why this matters
Revenue is what a company brings in. What shareholders own is a claim on what's left after the company pays for everything. Two companies with the same revenue can keep very different amounts, and the difference says a lot about the business. This lesson follows STU Corp's $400 million of revenue down to its profit.
The layers of cost
An income statement works like a set of stairs. It starts with revenue and subtracts costs in steps, with a measure of profit at each landing.1
- Cost of goods sold. The direct cost of making or buying the products a company sold during a period, such as materials and factory labor. Also called cost of sales. Glossary: the direct cost of making or buying what was sold. For STU Corp, that's filter materials, plastic housings, factory wages, and running the factory. Revenue minus this cost is Gross profit. Revenue minus the cost of goods sold: what's left after the direct cost of making or buying what was sold. Glossary.
- Operating expenses. The costs of running a company that aren't tied directly to making each product, such as research, marketing, and office salaries. Glossary: the costs of running the company that aren't tied to making each unit, such as research and development, marketing, sales staff, and head office salaries. Gross profit minus these is Operating income. Gross profit minus operating expenses: the profit from a company's core business, before interest and taxes. Glossary, the profit from the core business.
- Interest and taxes: interest on the company's debt, then income tax. What's left is Net income. The profit left for shareholders after all costs, interest, and taxes. Also called net earnings, or the bottom line. Glossary, the profit that belongs to shareholders. It's the "bottom line," literally the last line.
| Line item | This year |
|---|---|
| Revenue | 400 |
| Cost of goods sold | (200) |
| Gross profit | 200 |
| Research and development | (20) |
| Selling, general, and administrative | (100) |
| Operating income | 80 |
| Interest expense | (6) |
| Income before taxes | 74 |
| Income tax | (16) |
| Net income | 58 |
STU Corp is fictional. Amounts in $ millions. Numbers in parentheses are subtracted.
The rest of this lesson is for members
Still to come in this lesson: Margins, Fixed costs, variable costs, and operating leverage, Compare within an industry, the key takeaways, and 2 quiz questions with explanations.
Membership opens every lesson in the curriculum, the capstone projects, the interactive tools, and the members-only channels in the Hyperion Entities Discord. The first lesson of every module stays free.
Go deeper
- Costs, Scale, and ProfitEconomics for Investors (depth track)
- Pricing PowerEconomics for Investors (depth track)
- Is It Profitable?Part 3: Understanding Businesses
Notes and sources
- U.S. Securities and Exchange Commission. Beginners' Guide to Financial Statements. Checked 2026-09-30. Back to text
- Aswath Damodaran, NYU Stern School of Business. Margins by Sector (US), data as of January 2026. Checked 2026-09-30.