How to calculate margin: take your selling price, subtract the cost of goods sold, divide by the selling price, and multiply by 100. The formula is Margin (%) = [(Selling Price − COGS) ÷ Selling Price] × 100. For a product you sell at $50 with a $25 cost, your margin is 50%.

The core difference is simple: markup is the amount you add to your cost to set a selling price, while margin is the profit you keep as a percentage of the final selling price.