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strange_doings ([personal profile] strange_doings) wrote2014-09-17 04:41 pm
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A Better Pleated Skirt Tutorial

Pleated skirts are a staple of a large segment of anime cosplay - nearly every genre within anime as well as a bunch of video games feature school uniform designs and/or daily wear with pleated skirts. I don't get contracted often for them, maybe once a year, so every time I get a new order for something that has a pleated skirt in the design, I find I need a quick refresher on the methodology. Not the technique, no, but the math. How long of a rectangle do I need to cut and sew to fit into the waistband?

The problem is, most tutorials online are missing a tiny yet crucial piece of information: that the size of the pattern piece is entirely dependent on the quantity of pleats that will fit into the waistband. And the quantity of pleats, in turn, is entirely dependent on the size of those pleats. In some cases, there's also the extra variable of the type of pleat that throws your math completely off. Most tutorials don't take any of that into account, and thus, the math is completely wrong for most people.

Most tutorials assume you only want 1" knife pleats in your skirt. For a very basic uniform skirt, or a professional-looking daywear skirt (or a couture skirt, fashion skirt, etc), this will do. In that case, the general math of 3" of fabric per 1" of waistband is accurate enough. But what happens if you look at your character and 1" is way too tiny of a pleat? What if you need 1.5" or 2" pleats? Worse, what if you want box pleats instead of knife pleats? You're screwed, right? No you're not!

I'm also putting this into words for my own sake, so that the next time I get an order for a pleated skirt, I'm not fruitlessly googling my way to failure. The key with pleated skirts is to accurately gauge how many pleats will fit into your waistband - and, in the process, determine how large those pleats need to be in order to make you look exactly like the character. The math is a lot trickier, and I'm bad at explaining without diagrams/photos so bear with me for a bit.

We'll use my current waist size as an example, as it's 36" - an even number divisible by 2 as well as 3. Not counting the seam allowance, my waistband at finished size will be 36, so the usual tutorial will tell me for 1" knife pleats, I need 3x that number, or 108", as the length of my rectangle. For now, we're only going to talk about length, as width isn't important until you're looking at how long the skirt will be and thus how much fabric you need. Suffice it to say, regardless of whether you're buying 45" wide fabric or 60" wide, to make any pleated skirt you cut a number of rectangular panels to sew together to make one really long panel that equals, in this case, 108".

But I look at my reference and the skirt isn't made up of a lot of teeny pleats, but rather a handful of very large pleats. A little toying around tells me I want 2" pleats, I think those will look the best. So why doesn't the math work out? Aren't pleats still 3x the fabric for 1 pleat? For knife pleats, yes, they are - but now, instead of each pleat requiring 3" of fabric, each pleat requires 6" of fabric. So that's the number I multiply by my waist size, right? Wrong! Visualize for a moment. A 2" pleat will not magically fit 1" of waistline. That covers 2 whole inches of your waist. Already, the math is looking crazy, isn't it?

The first step is to look at my finished waist size and determine how many pleats will fit into it. I have a 36" waist, so if my pleats are 2", that's 36/2 or 18 pleats total. That is the number you multiply by the total amount of fabric per pleat, which is 6". So it comes out to 108". Oh my, it's the same as the other formula! Yes, but only because my example was 36. What if my waist size is 32? The number of pleats is 16, so if each pleat takes 6" of fabric, then my rectangle needs to be 96" long. If my waist size is 40, the rectangle needs to be 120" long. However, these two new examples leave us with a bit of a quandary: divide the waist measurement by 6" and you'll see that you're going to end up with a partial pleat at the end! This is actually a problem, one that needs to be solved by either fudging all the pleats around the entire skirt until you end up with the final pleat more or less matched up with the first pleat, or creating a single, smaller pleat at the seam where your zipper will go in. The latter is faster but sort of a pain if you don't want people to notice that one hinky pleat sitting there in plain view. The former takes either more math or just a lot of re-re-re-pinning your pleats until you give up and iron the bastards down.

So, while the numbers will tell you how much fabric you need (not including seam allowances), they don't tell you what kind of a pain in the butt your pleating is going to be. And once you start getting into 1.5" or 1.75" or 2.25" pleats, then it all goes to hell. Using the original 36" waist example, I can get 20.57ohmygodwhatisthisnumber pleats into my waistband. That's not a huge help, is it? Suffice it to say, I can get at least 20 pleats in with some leftover gap of fabric at the zipper. Each pleat now takes 5.25" of fabric, so I can cut my rectangle at 105" and just sort of pleat it and see what happens. It could be hilarious or it could make me swear off tailoring forever. Either way, that number is very different from the basic 3x waistband math. And, unless you have a waist size that is evenly divisible by 2 and 3 (30, 36, 42), you're going to end up with half or a third or two-thirds of a pleat at the end, and you'll have to go back and figure out what you're going to do with that partial pleat in order to make the skirt look nice.

Really, I feel for anyone with a 31" waistband, or worse, 45", because the math can only really get you into the ballpark and the rest is just fudging all your pleats until they're all sort of even (for you OCD types) or dealing with that one tiny partial pleat at the zipper. Most skirt patterns suggest the zipper should sit at the hip rather than the center-back, so it's going to be visible no matter what you do.

What about box pleats? Well, they're a different animal entirely, math-wise, because each box pleat is made up of two knife pleats facing opposite directions, meeting in the middle. Each pleat is not a nice neat 1" made up of 3" of folded fabric, a complete box pleat is actually 6x the pleat size - but your finished pleat, on the outside, comprises double what a knife pleat would. So where a 36" waist can handle 18 2" knife pleats, it can only handle 9 2" box pleats, because each box pleat is 2"-><-2", or 4". Which, okay, not so bad. But that means each complete box pleat is 12" of fabric. Which, on a 36" waistband, is okay, because 2, 3, 4, and 12 all fit nicely into that measurement. And only that measurement. For a 31" waist? Not even close. The bigger the box pleats, the harder it is to fit them evenly into a waistband without having half a pleat left over. Or worse, a third of a pleat. How would you like a gap at the zipper of 3" of wasted fabric? I sure wouldn't.

So, the 3x waist measurement formula might allow you to estimate how much yardage of fabric to buy (see below) but it won't help when it comes time to cut your skirt panels and start pleating them. Instead, you want to use the desired size of pleat to figure out how many of said pleats will fit into your waistband, and if there's any kind of remnant, then you get to decide how to incorporate the remnant. It might mean making the pleats slightly larger or slightly smaller than planned in order to take up the excess. Which, really, is not a disaster, because when you look at your character reference, the size of the pleat isn't going to be a hard and fast rule. You won't be able to count the number of pleats the artist drew in and triangulate them to your own waist, because art is inconsistent and it might mean that in the "real world" your pleats are 5" wide, which is ridiculous. You're already guessing, based on how the pleated skirt looks on you, with your torso length, leg length, etc. So, there is no harm in cutting with the mathematical guesstimate, pinning up the pleats, and trying on the skirt to see if the pleats look too large or too small before settling and stitching them down.

Now that you're good and confused, let's recap something simple: estimating how much fabric to buy. Whether you go by a very simple 3x waist measurement, or you go ahead and figure out pleat quantity per your waist size and multiply that by 3 (or 5.25, or 4.5, or whatever your pleat size comes out to), you have a number that indicates how long of a rectangle will be pleated into your waistband. But most fabric isn't anywhere near that big, it's usually 45", 54", or 60" on the bolt, and often considerably less than that once you wash it. So, in order to make a skirt, you need to cut multiple panels with this measurement: L=width of fabric, W=how long you want the skirt to be plus seam and hem allowance. You sew those panels together and then pleat them into the waistband. So, the quantity of fabric depends on how many of those panels you need, plus a waistband. As long as your waist size is less than the width of the fabric, all you need is an extra, say, 5-6" max at the end. If your waist size is larger, you'll need to piece fabric together, so you'll need more.

Now, if you've decided that you want your skirt to be 12" long, you plan to only sew 1/2 inch into the waistband at the top, and are doing a rolled hem that totals 1" at the bottom, then the width of each skirt panel will be 13.5". So, let's say that you figure out that you'll need about 2 and a half panels to get your length measurement close. Well, if you're cutting panels that are the full width of the fabric, there's no sparing a half a panel here or there, it's all whole numbers. So, 3 panels. Each one is 13.5" wide. That gives you a total of 40.5 inches, which is a little over a yard. Don't forget your waistband! So say maybe 45 or 46". That means you'll need to buy maybe a yard and a half at the most. If you're pre-washing the fabric (and you really should, even if it's polyester), there could be shrinkage that will affect your plans when you cut - maybe now instead of being 60" wide, the fabric is 57. Plus, you have to factor in seam allowance for sewing those panels together. So maybe now instead of exactly two panels, you're looking at 2 panels plus a third panel that turns out to be 15" long. At least you planned ahead and bought enough yardage that you're not suddenly crying!

Math is hard, and even the simplest of garments can be deceptively difficult when it comes time to sew!

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