Determine the difference between contribution margin and Gross margin.

Contribution margin is calculated by deducting variable cost from the selling price and gross margin is calculated by deducting directly attributable cost from selling price.

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