The math behind pleating

1357617391907There is a LOT of math involved in knitting, crochet, and sewing and my mom is always asking me for help with her crafting. Her latest request was for help sizing some pleats. The plan was to take a wide piece of cloth and sew it onto a crocheted edging for a dress. Her problem was that she didn’t know how to mathematically determine the size of each pleat. Without some basic understanding of math, she would have been running a rince and repeat / trial and error for days before she found the right pleat size!

So, here’s what we did:

First, measure the width of the piece of fabric you want to pleat and then measure the width you want that fabric to be (in this case, the same size as the crocheted edging).
Full fabric width = 42 in.
Final width = 19 in.

Next determine how many pleats you want (we choose 14) and how much fabric each pleat will take up.
42 in (full fabric width) / 14 (number of pleats we want) = 3 inches.
You can adjust the number of pleats you want to get a reasonable number (the 3 inches) or to adjust for your desired effect.

Now lets run the math to determine the difference between those two numbers and how wide each fold should be.

Subtract 19 from 42 to get 23 (this is how much fabric you need to “pleat” away to “shrink” the 42 inches to the desired 19).

Divide the excess width (23) by 14 (the number of pleats you want) to determine how much fabric to pleat away on each pleat.
23/14 = 1.64

Now we have segmented a 42 inch width into 14 equal area’s of 3 inches with a 1.64 inch fold area! All we have left to do is mark up the cloth, and iron and stitch into place.


Diagram of the final pleats.

Happy pleating!

For those more math minded folks, here’s a formal equation for pleating:


Damien is a college student with a love for math. He tested right out of college level algebra and trig on his first day, and jumped straight into calculus. After he left his student job as a cleaning assistant (math students, bleach, and science lab floors don't mix too well), he started tutoring, and quickly became a favorite among the students. Damien tutors because it gives a more interpersonal connection than classroom teaching, and allows for more time to be focused on the student's needs. It helps weed out any specific problems the student has, while improving their skills and overcoming barriers. He uses his experiences as a tutor to make friends and hone his math skills. When he isn't learning math, Damien likes to solve Rubix cubes (he can solve one in under two minutes), take parkour classes, and play Skyrim. If you want to know more about him, drop him a line!

Posted in Math for Everyday Life

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Damien did a great job guiding me through the learning process of algebra!

Algebra student