To achieve a gross margin or gross profit percentage of 25%, you will need to mark up your product's cost by 33.333%. The following illustrates how this is calculated.

Assume a product has a cost of $75 and a selling price of $100. Since the gross profit is defined as selling price minus the cost of goods sold, this product will have a gross profit of $25 ($100 minus $75). The gross margin or gross profit percentage is 25% (gross profit of $25 divided by selling price of $100). The mark up of $25 on the cost of $75 equals 33.333% ($25 divided by $75).

Let's prove this with one more example. Assume you have a product that you purchased for $9. If you mark it up by 33.333%, you will have a markup of $3 and the product will sell for $12. The income statement will show a sale of $12 minus its cost of $9 for a gross profit of $3. The gross profit of $3 divided by the selling price of $12 equals a 25% gross margin or gross profit percentage or gross profit ratio.