Gross Margin is the Gross Profit as a percentage of Net Sales. The calculation of the Gross Profit is: Sales minus Cost of Goods Sold. The Cost of Goods Sold consists of the fixed and variable product costs, but it excludes all of the selling and administrative expenses.

Contribution Margin is Net Sales minus the variable product costs and the variable period expenses. The Contribution Margin Ratio is the Contribution Margin as a percentage of Net Sales.

Let's illustrate the difference between gross margin and contribution margin with the following information: company had Net Sales of $600,000 during the past year. Its inventory of goods was the same quantity at the beginning and at the end of year. Its Cost of Goods Sold consisted of $120,000 of variable costs and $200,000 of fixed costs. Its selling and administrative expenses were $40,000 of variable and $150,000 of fixed expenses.

The company's Gross Margin is: Net Sales of $600,000 minus its Cost of Goods Sold of $320,000 ($120,000 + $200,000) for a Gross Profit of $280,000 ($600,000 - $320,000). The Gross Margin or Gross Profit Percentage is the Gross Profit of $280,000 divided by $600,000, or 46.7%.

The company's Contribution Margin is: Net Sales of $600,000 minus the variable product costs of $120,000 and the variable expenses of $40,000 for a Contribution Margin of $440,000. The Contribution Margin Ratio is 73.3% ($440,000 divided by $600,000).