Try on your skirt and measure to your desired length.

Mark the preferred length with chalk.

The first picture shows where the preferred length mark matches up. For this skirt, the added length is 6 inches.

Next, measure the width of the skirt.

For this skirt the width is 19 inches.

Purchase necessary material while keeping in mind the dimensions of length and width that you will be adding. An easy way to calculate how much material is needed is to multiply the width dimension by 2 and then multiply the length dimension by 2. It may be beneficial to purchase extra material.