Gross margin is the difference between revenue and cost of goods sold, or COGS, divided by revenue, expressed as a percentage. Generally, it is calculated as the selling price of an item, less the cost of goods sold (production or acquisition costs, essentially). Gross Margin is often used interchangeably with Gross Profit, but the terms are different. When speaking about a dollar amount, it is technically correct to use the term Gross Profit; when referring to a percentage or ratio, it is correct to use Gross Margin. In other words, Gross Margin is a % value, while Gross Profit is a $ value.

Gross Margin is a type of profit margin, specifically a form of profit divided by net revenue: for example, gross (profit) margin; operating (profit) margin; net (profit) margin; etc.

Purpose

The purpose of margins is "to determine the value of incremental sales, and to guide pricing and promotion decision."

"Margin on sales represents a key factor behind many of the most fundamental business considerations, including budgets and forecasts. All managers should, and generally do, know their approximate business margins. Managers differ widely, however, in the assumptions they use in calculating margins and in the ways they analyze and communicate these important figures."