An Economic Case for Larger Pattern Sizes

Imagine you are a pattern maker. You have a great design all worked out. But what sizes should you include in your pattern?

You might start by looking at what other pattern makers are doing. Then you might look at what standard size ranges are being used by ready-to-wear clothing manufacturers and large commercial pattern makers. But a small pattern maker can’t always afford to make every pattern in every size, so how do you choose?

A Look at the Numbers

The body weight of adult women follows what is called a standard distribution. If you charted out the number of people by their body weight, it would make a curve. There would be a lot of people in the middle of the curve (around the average weight), but not many people out at the ends of the curve (with very low or high weights).

According to SizeUSA, as of 2004, the average bust size in the US was 40″. That translates to roughly a size EUR 44, or US pattern size 18. That’s the centre of the curve.

Indie Pattern Makers

What many independent pattern companies choose to do, is offer their patterns in sizes 6 to 18 (or average). If you chart that out, you can examine what is called “the area under the curve” and use this to calculate the percentage of the population in that range.

For independent pattern companies that offer their patterns in sizes 6 to 18 (the green area under the curve), that area is about 43% of the total population. That means that if you make a pattern available in that size range, only 43% of the general population can use your patterns.

Indie pattern range
Here the green area represents the size range sometimes chosen by Indie pattern designers. About 43% of the population can use these patterns.

That’s not a huge number, so you might think about extending your range of sizes. But in what direction? If you look at the chart you can see that by extending the range down, say two sizes, you make the area under the curve just a little larger, but if you extend the range up by the same number of sizes, you make that area much larger. In other words, you can find more buyers by adding sizes nearest the centre of the curve (size 18), then at the ends.

Big 4 Pattern Makers

That’s what commercial pattern companies do for their regular pattern range. Often, they offer patterns in sizes 6 to 22. With that range, about 63% of the population can use their regular patterns. They’ve just increased their population of potential buyers by about half. But instead of 7 sizes their range includes 9 sizes.

Here the green area represents the size range used by Big4 pattern companies.
Here the green area represents the size range used by Big4 pattern companies in their regular size range of 6-22. About 63% of the population can use these patterns.

An Ideal Limited Pattern Range

When you produce a pattern, there is an additional cost for producing and grading each size. Not every pattern maker can add extra sizes. So lets assume that as an independent pattern maker, you can only afford to draft seven sizes. Which should they be? In order to include the largest number of potential buyers, you should centre your seven sizes around the average size. If you include sizes 12 t0 24, 56% of the general population can use your patterns. In other words, by shifting the range of patterns you are providing up by a couple sizes, you can make more money at no extra cost.

Ideal pattern 7-size range. About 56% of the population can use these patterns.
A limited ideal pattern size range. There are still only 7 sizes, but now 56% of the population can use these patterns.

Our average weight has been increasing over the past several decades. In the 1940s and 1950s, when standard clothing sizes were developed, the average bust measurement was 35″, about a size 12-14.

If you look at the Big4 pattern makers, this is the centre of their current range of sizes. Most likely, they originally organized their pattern size range to centre around the average size (in the 1940s and 1950s), in order to maximize profits. But since then, our bodies have grown out of that ideal range, and the Big 4 pattern companies have not adjusted.

If you look at the small range that many small independent pattern companies are using (6-18), they are also centring their size range around this outdated average, just like the Big4 pattern companies. But they don’t have the historical reason to do so.

A Sample Extended Pattern Range

And what would happen if you matched the size range on both sides of the average? What would happen if you offered sizes 6 to 18, but then also offered sizes 18 to 30? You’re patterns could be used by 86% of the population. You would double your population of potential buyers (and presumably your profits). Of course now you would also have to draft an extra 6 sizes. And of course, you can always extend that range even further.

Here the green area includes sizes 6 to 30.
Here the green area includes sizes 6 to 30. It’s the equivalent of S to 3X. About 86% of the population can use these patterns.

And would that extra segment of the population buy your patterns? It’s hard to predict. But assuming the patterns were well drafted, and fashionable, you would be adding a population of potential buyers that are underserved by both large commercial and small independent pattern makers, but also by the ready-to-wear clothing industry.

Statistical Caveats
This model of pattern sizing is approximate and depends on a number of assumptions.

Human body weight follows an approximately normal distribution, so it’s logical to assume that clothing sizes do as well, but they might not. That data has been compiled by private companies, but it isn’t publicly available.

This model assumes that clothing sizes vary by equal amounts along the curve, that measurements like bust size and body weight are perfectly correlated, but that isn’t necessarily the case.

Nevertheless, it’s logical to assume that the model would be a good approximation of size distribution in the population and the calculations shown here would hold up.

So what sizes should you include in your pattern?

Based on time and budget constraints, determine how many sizes you can draft, test, and print. Then centre those sizes around the average, size 18 (EUR 44 or L with bust 40″), with an equal number of sizes above and below that point. (And yes, size large, is in fact average).

Of course, this takes into account only cold hard economics of choosing a size range. There are many reasons, besides profits, that would lead to different choices. In a perfect world, all patterns would come in all sizes – and they would all look amazing! (perfect world right?)

Your thoughts are welcome in the comments!

How to Grade the Kelly Skirt

The Kelly skirt by Megan Nielsen
The Kelly skirt by Megan Nielsen.

So you want to make Megan Nielsen’s Kelly skirt, but it doesn’t come in your size? Whether you need a plus size like XXL, or 3X, or a smaller size, like XXS there is an easy solution – grading the pattern.

What is Pattern Grading?
Grading a pattern just means to take a pattern up or down a size, or more. There are many ways to grade a pattern, and lots of articles on how to do this. It can be a complex process, depending on the pattern. But it doesn’t have to be. In fact, if you have never graded a pattern, the Kelly Skirt is the perfect one to start with.

This skirt fits waists between 26 and 34 inches (66-86 cm). In commercial pattern sizes, that translates roughly to sizes 12 to 20. That is a pretty good range, but we can easily extend that range.

This week I published my own version of the Kelly Skirt and I mentioned that it is an easy pattern to grade. I recently had my fourth baby, and although I would normally be a size large in the Megan Nielsen size range, my waist is (temporarily I hope!) larger than the largest size included in the pattern. I graded the pattern up a size. I am not an expert pattern grader, this is just the way I graded the pattern. Since it worked out well, I thought I’d share.

Getting Started
In order to grade the pattern, you will need to trace the pattern onto tracing paper, with a few simple modifications. If you have never traced a pattern before, I suggest you read “How to Trace Sewing Patterns” by Sunni on a Fashionable Stitch. There are also some good photos of the process here.

You will need tracing paper, a pencil and a ruler.

A Little Math
You will start by comparing your measurements to the closest pattern size. You can ignore the bust measurement completely. Because the skirt is gathered and has a fair bit of room in the hips, in most cases, you can just look at the waist measurement. However, if you have very large hips, compared to your waist, you may need to make more complex modifications. For this tutorial, we’ll assume your hips and waist are roughly proportional.

Kelly skirt pattern back.
What measurements to look at when grading the Kelly skirt.

Going Up a Size
If you are going up a size, compare your waist to body measurements for the largest pattern size. The waist measurement given for the XL size is 34 inches. My waist is 37 inches at the moment. That means I need to add 3 inches to the XL size.

Make sure you are looking at the body measurements and not the finished garment measurements. The finished garment measurement won’t be skin-tight, it should have some ease or breathing room, so that the clothing will be comfortable to wear. This pattern has around 3/4 of an inch of ease at the waist. Professional pattern graders adjust the ease in very precise ways, but we’ll just use the ease of the closest size (XL or XS).

Going Down a Size
If you are going down a size, compare your waist to the to body measurements for the smallest pattern size. The waist measurement given for the XS size is 26 inches. If you have a 24 inch waist, you would need to subtract 2 inches from the XS size. Again, make sure you are looking at the body measurements and not the finished garment measurements.

Modifying the Pattern Pieces
There are only 5 pattern pieces in the Kelly Skirt.

Kelly skirt
There are only five pattern pieces for the Kelly skirt.

Pocket Facing and Pocket Lining
You will trace the pocket facing and pocket lining as they are. These two pieces don’t change when the skirt size changes.

The Waistband
The waistband is a single piece that circles the waist. In the XL size, this piece is made for a 34 inch waist. Because I have a 37 inch waist, I need to add 3 inches of length to this piece. I added the length to the XL size at the end without the markings, just because it is a little easier that way. Don’t forget to transfer all the markings to your tissue paper. If you are going down a size, subtract the amount you need from the XS size. This will shorten the waistband.

Keep in mind that the piece won’t measure exactly 37 inches after my modification. That is because the length of the pattern piece also includes seam allowances.

I write the changes I’ve made directly on the tracing paper as a reminder.

Kelly skirt waistband
The modified waistband for the Kelly skirt.

The Skirt Front and Skirt Back
The skirt front and skirt back need to be modified as well. I need to add 3 inches, but I need to split this amount between the two seams that join those pieces together. That means I need to add 1.5 inches to each seam, and 0.75 inches to each pattern piece at that seam.

Kelly skirt
Modifications to the back of the Kelly skirt.

The skirt back is cut on the fold. I just extended out the side that is not on the fold by o.75 inches. Because the piece is on the fold, that amount fill be added to each side of the pattern piece.

You will also have to move the markings for the pleats on the skirt back. If you don’t, the pleats might look a bit odd, and strangely placed. If you are going up a size, starting from the markings for the XL size, for two inches that you added to the waistband, move the pleat markings out, away from the fold, by 1/4 inch.  (The pleat markings are more precisely spaced than 1/4 inch intervals, but this number will serve as a good approximation for us.) If you are going down a size, starting from the markings for the XS size, for two inches that you subtracted from the waistband, move the pleat markings in, toward from the fold, by 1/4 inch. There are three lines that need to be moved.

Kelly skirt front
Modifications to the front of the Kelly skirt.

The skirt front is in two pieces. I extended out the side with the curve for the pocket by 0.75 inches. This adds 0.75 inches to each piece. Again, I moved the markings for the pleats over exactly the same way as for the skirt back.

Kelly skirt pattern changes.
These are the changes I made to the Kelly skirt.

What about the skirt length?
If you are going down a size, it’s probably a good idea to keep the length of the XS size, unless you are also shorter than average. After all, it is easier to take the hem up a little more than to be stuck with a skirt that is shorter than you were expecting.

If you are going up a size, you can probably also stick with the XL length, unless you are also taller than average. I used the length of the XL skirt and I’m quite happy with the results. However, you need to make sure that there is enough skirt so that when you are sitting, you can sit on the skirt, and not on the hem. If you are quite a bit larger than the pattern XL size, and your pattern modifications are substantial, you may also want to add some length so that you can sit comfortably. The finished skirt length of the XL size is 23 inches. Compare this to a skirt you own, to see if this is sufficient.

What next?
That’s it! Now assemble the skirt following the instructions.

Kelly Skirt
Kelly Skirt by Megan Nielsen in linen with black piping.

I hope you have found this useful. If you have any tips for making this process a little easier, please leave them in the comments.