In the early days of my career as a designer, I disliked or even feared math. Then I met a great pattern drafting instructor who dispelled my fear and helped me to fall in love with numbers and formulas. Those of us who have worked on pattern drafting know how important it is to calculate correctly in order to create a well-balanced pattern that fits well on the body.

I’ll introduce you to a simple geometry formula that can help you easily create eight different skirts. Each is constructed from pattern pieces shaped like part of a circle. To draft the patterns, you need to take two measurements: your waist circumference and the desired skirt length. Because there are only six steps to create the pattern, as you do this more, you may find that it is easier to draw cutting lines on the fabric rather than drafting a pattern.

I will show you how to calculate and draft the pattern for full circle, half-circle, medium bell, and full flare (generous A-line) skirts. The same directions can be applied to calculate and draft the rest of the skirts presented in the illustration on p. 58. The skirt patterns and samples shown use a 26-inch waist circumference and 21-inch skirt length.

Note the four essential numbers

To make these skirts, you need only four numbers. These numbers are put into a simple formula to create the skirt patterns.

Waist circumference

Measure your waist circumference. In this case, it should be the circumference of where you want the waistband of the skirt to sit, most likely at the natural waist. Divide this measurement in half to get the Half-Waist Circumference (HWC).

Factor

The factor (F) is a mathematically derived number, and it is used in geometry to calculate radius and build circular…