A reader got in touch yesterday and asked me about how I worked out the pleats in my box pleated skirt so I thought I’d post the info for doing just that .
This is the formula I like for working out box pleat markings and how much fabric it will take:
(A) your waist measurement divided by total number of box pleats desired= what each pleat face will measure
(B) your waist measurement multiplied by 3= total amount of fabric needed (excluding seam allowances) because a box pleat takes 3x its width in fabric.
For example if you want a skirt with 6 box pleats (3 across the front and 3 across the back) and your waist is 72 cms the formula would look like this:
(A) 72 cm waist divided by 6 pleats = 12cms which is the width of each pleat at the waist and the spacing you need to mark 3 times to create each pleat. So for 6 pleats and a 72cm waist you’d mark ten 12cm spaces for both the front and back. You’re thinking hmmm but 3×3 is 9 , yes but you need a line for the ninth mark to pleat over to so thats why you need to mark a tenth.
(B) 72 cm waist x 3 = 216cm is the total amount of fabric needed though you do need to add some extra for seam allowances. Say add 5cm for seam allowances and there you have the running meterage you need: 2.21 metres for cutting along the selvedge if using a striped fabric like in the red and white skirt above that I did for Making magazine a few months ago. That skirt only has one seam in the left side where the zip was inserted.
In -A- you can use the number of pleats you like i.e. 6, 8 or 10 etc. Or use an odd number like 7 or 9. An even number of pleats tends to sit better around a body and then you get seams at the sides for adding pockets in but that may be more about my personal preferences rather than being a fact.
The diagram shows the directions to make the box pleat folds in.
To cut across the fabric so your skirt is made from two pieces like my orange linen one with two side seams (where you can add in-seam pockets) then the meterage you need would be twice the finished skirt length you want plus hem and waistband seam allowances. Regarding fabric width to cut it like this- larger waist sizes will need wider width fabrics or more than two seams in the skirt. To estimate the width needed for your waist size divide the running meterage total you calculated in back in -B- in half. This gives you an idea of what width fabric you’ll need for each of the two halves of your skirt. As a basic guide: waists 62cm -72cm should fit across 114cm width fabric, 77cm need 125cm width and 82 & 8cms require 140cm width fabric. As a work-around for larger waist sizes or if you’re working with a very narrow fabric the skirt could be cut in 3 or 4 panels with the seams hidden in the back folds of the pleats. Or go back to cutting it along the length of the fabric so you aren’t restricted by a limited width fabric.
It’s a good idea to test marking and folding it out on a long strip of paper first if you are unsure of any aspect of this.
Thank you to ‘iconoplast’ and Nico who both helped me see the way to simplify my calculations from A-B-C to just A & B.
Sewing up the skirt is just a matter of pinning and stay-stitching all the pleats in place. Sewing the right side seam closed and adding a zip in the left one. Adding a waistband on with a button or hook and bar to close and sewing up the hem. You can knock a skirt out in a couple of hours.