Welcome back, dear readers. Let's talk about pleats, what are they and how do we calculate them to get the results we want. Pleats can be used for functionality and style. They can be added to almost any part of a garment, resulting in an interesting feature if used right.
What are pleats?
Pleats are folds made in a garment to add fullness and create shape. They are usually used as an alternative to darts and gathers. There are 3 main types of pleats.
Knife pleats - Each pleat is one fold and all folds are made in one direction uniformly
Box Pleats - Each pleat is two folds, with the folds facing away from each other
Inverted pleats - Each pleat is two folds, with the folds facing towards each other
Box and Inverted pleats are really the same thing, but there is a shift in the focal point of the design.
How to get the results you want
Now, if you have the luxury of extra fabric, you can simply fold the pleats by eye in whatever combination you want, this is usually done if one is draping on a dressform, using a patterned piece of fabric (like plaid), or making a kilt or other similar traditional garment. But there are times when you need to plan out the pleats first, such as when you have limited fabric, or there is a particular number of pleats you need for your design.
First, you need to decide which of the 3 things below, is important for you to get the pattern you want, before you can make your calculations
Only the number of pleats - Here you need to measure the area where the pleats are to be made and then divide it by the number of pleats you want, this will tell you the size of the pleats.
E.g. a skirt waist (32 inches) divided by the number of pleats (8) = width of pleats (4 inches). From this you can calculate the folds needed to create the pleat.
Only the width of pleats - Here you need to measure the area where the pleats are to be made and then divide it by the width of pleats you want, this will tell you the number of the pleats.
E.g A skirt with 1-inch wide knife pleats. The skirt waist (32 inches) divided by the width of pleats (1 inch) = number of pleats (32). From this, you can calculate the folds needed to create the pleat.
Both the size and the number of pleats needed - similar to the above, here you have to multiply the width of the pleat (4inches), by the number of pleats (8) which equals 32inches. If this was for a 35-inch waistline, you will know that there will be 3 inches extra that will be unpleated and you can plan your design accordingly.
Rule of threes
This rule applies to all 3 kinds of pleats mentioned above. If a pleat is 2 inches wide, then you reserve 6 inches for the pleat. Allotting 2 inches for the visible part and 4 inches for the folds. Similarly, If the pleat is 4 inches wide, then you would reserve a total of 12 inches.
How to Calculate Pleats
A skirt with box /inverted pleats by number of pleats
35 inches waist divided by 10 Pleats = 3.5inch wide pleats.
Using the Rules of threes, it will be 3.5 x 3 = 10.5 inches per Box /Inverted pleat
Therefore, 10pleats x 10.5 inches = 105inches.
Add the seam allowance/zipper allowance of 3inches. In total, we need 108 inches for the waist of the skirt.
For yardage, we have 108 divided by 36 = 3yards
A skirt with knife pleats by the size of pleats
28inch waist divided by 1inch wide pleats = 28 pleats
Using the Rules of threes, it will be 1 x 3 = 3 inches per knife pleat
Therefore, 28pleats x 3 inches = 84 inches.
Add the seam allowance/zipper allowance of 3inches. In total, we need 87 inches for the waist of the skirt.
For yardage, we have 87 divided by 36 = approx. 2yards 15 inches
Variations on fullness
By using the technique above, you are gaining the maximum amount of fullness that the pleat will allow without overlapping in any way. You can reduce the fullness by reducing the width of the folds that are hidden under the main pleat while achieving the same look.
Earlier I mentioned that if a pleat is 1 inch wide, then reserve 3 inches for the pleat. Allotting 1 inch for the visible part and 2 inches for the 2 folds. This is a 1:1:1 ratio. To reduce this, we will maintain the 1 inch for the pleat and reduce the 2 inches by half i.e. 1 inch making it a 2:1:1 ratio instead. So instead of each pleat needing 3 inches, it will now need 2 inches. From here you can figure out your total length of fabric.
Closing Thoughts
This brings us to the end, but I want to point out that I didn't cover more complicated combinations of pleats, simply because they are all based on these foundation steps.
Appendix.
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Well now that I published the comment, I can see the white stars beside the Add a Rating. Maybe I need new glasses - haha.
Very good information and well illustrated! I have copied this to add to my sewing binder so that it is easy to access when I want it. thank you for covering this topic so well! ps I wanted to add a rating but couldn't get the stars to transfer.