Profit margin is the amount by which revenue from sales exceeds costs in a business, usually expressed as a percentage. It can also be calculated as net income divided by revenue or net profit divided by sales. For instance, a 30% profit margin means there is $30 of net income for every $100 of revenue. Generally, the higher the profit margin, the better, and the only way to improve it is by decreasing costs and/or increasing sales revenue. For many businesses, this means either increasing the price of products or services or reducing the cost of goods sold.

Profit margin can be useful in several ways. For starters, it is commonly used as a way to gauge the financial health of a business. For instance, a year that is off track with respect to typical profit margins in past years can be an indication of something wrong, such as the mismanagement of expenses relative to net sales. Secondly, the profit margin is a measure of efficiency, as it helps answer the question: how much profit is received for each dollar earned as revenue?