Why larger sizes cost more or Size is nothing but a number

Inspired by a recent comment:

Please explain to me why lines that sell the exact same clothes in a 6 to a 20 charge more for the 16-20. In my example it is the exact same style and brand (pinup style clothing which tend to fit plus sizes well). PLEASE help me understand as I find it entirely perplexing!

The answer to this question may seem intuitive but the context is that she read Why existing manufacturers don’t add plus sizes in which we said the costs of adding on a plus size line were considerable, on the order of adding another division. Since the manufacturer she mentions already tacks on larger sizes to the standard sizes they offer, I can see she has a point.

It goes without saying that Lisa is new in these parts because she has not learned I cannot tell you the time without also explaining how to build the clock. Thus opens this discussion circuitously in which I explain that size is nothing but a number. 

Costing and pricing is based in part on fabric use. Because costing is so complex, it is not possible to cost per size. The costs of a size medium is used as an average to determine the cost of each unit produced. Some sizes are a little smaller and use less fabric and some sizes are a little larger and those use more, so it works out more or less. Consider:

  • Sizing in a line is based off the medium.
  • A medium is not a standard or a set of unchanging dimensions.
  • A medium is the midpoint of the range of sizes a manufacturer produces.
  • The medium is the average size sold. More mediums are sold than any other size.

Which explains why the measures of a medium are constantly evolving. If a manufacturer is selling more larges than mediums, it means their medium is too small. The large becomes the medium and the other sizes are adjusted accordingly.

In short, the size medium is determined by financial constraints rather than opinions of various individuals as to what they think a medium is or should be. Otherwise, the company goes out of business.

I realize some might think that one could use the large for costing instead of the medium but it doesn’t work for reasons I regretfully must omit at this time but for which you will or should thank me.

Here is the costing breakdown with respect to fabric use. Imagine if  you will, that all of the pattern pieces for the various sizes are laid out (we call this a “marker”) on the fabric. In the example below, I’m showing the pieces for sizes 6-14 which is what Lisa asked about.


If you notice, the size 10 (the medium) fits evenly. This is not because medium size patterns are specifically cut to fit fabric width this precisely only that the size 10 is the basis for costing, the zero point as it were. Costing wise, the 10 or medium is the average. Off to the right of the size 10, we have a size 12 and a size 8. Cost and fabric wise, the 12 costs +1 over the size 10 but the size 8 costs -1 so these two sizes average out to a ten. Off to the right of 8 & 12, we have the size 14 and the size 6. Again, the costs of size 14 are +2 over a size 10 but the size 6 is -2 as compared to the size 10. I really hope you all are following me.

You may also notice there are 2 mediums cut for 1 of every other size. This is also typical but not quite. Usually the order ratio is roughly 1-2-3-2-1 -or should be because this marks the distribution curve in the same way that the average IQ is 100. It is always 100 (IQ is also not static in the same way sizes aren’t). Anyway, if one’s sizing distribution doesn’t follow this bell curve, that means a whole lot of other stuff I’ve also written about (sizing analysis) and needs to be fixed. In other words:

    1 size 6 (or XS)
    2 size 8 (or S)
    3 size 10 (or M)
    2 size 12 (or L)
    1 size 14 (or XL)

Now I’ll return to Lisa’s question, why do the larger sizes cost more? Well, below is the fabric costing for those sizes. As the necessary point of comparison, I’ve included the size medium too (larger version of the image).
The point being that the size 16-20 do not fit neatly into the marker, accordingly there is waste and so the costs for those sizes are higher. Which brings me to another point.

A lot of women are upset that larger sizes in styles they like are not available. They say that the manufacturer should drop some of the smaller sizes and cut larger ones instead. Sure, that could happen but then we run into increasing the costs as the image above shows. This is the point, in order to cut larger sizes, you need smaller sizes on the opposite end of the spectrum in order to reduce fabric waste and thus cost.

Below is another marker I made showing sizes 0-20 (larger version)


The end result of this long drawn out explanation is that large sizes for which there is no correspondingly smaller size (to take up the waste left behind) will be more costly. The summary is that for this manufacturer to produce sizes 16-20 at no additional cost, they must also produce sizes 0-4. They probably don’t produce those sizes because that’s not their customer.

Even if a manufacturer does produce sizes 0-20, difficult decisions remain. You can’t cut a 20 without a 0 so the question becomes, which of those two sizes are the bigger driver and is it worth cutting extras of the opposite size for which there is no demand?

Let’s imagine you have 100 buys for the size 20 but only 50 buys for the size 0. You can’t keep costs down by overproducing 50 size 0’s so there will only be 50 size 20’s cut to match the order of the size 0’s. Now let’s explore the opposite situation. There are 100 buys for the 0 but only 50 for the size 20 -what happens? Call it discrimination all you will but all of the size 0’s will be cut because the extra size 0’s can fit in the space of the size 20. The amount of waste incurred by cutting size 0’s is less than the waste incurred by cutting size 20’s for which there is no size 0 to pair it with. In real life, one can cut 3 size 0’s for every 2 size 20’s so there is not as much waste as one would think. So again, it’s not discrimination against overweight people. It’s purely a matter of reducing waste and keeping costs as low as possible.

In truth, sizes are better described as medium plus or minus which is why size is literally an arbitrary number with very little meaning attached to it at all beyond sizing commensurate to other brands one hangs with on the same rack because customers become angry if there is too much size disparity between a 10 of Brand A and a 10 of Brand B. Sizes could be described more accurately like this:

  • Medium -2
  • Medium -1
  • Medium -0-
  • Medium +1
  • Medium +2

[This is theoretical, no professional pattern grader I know recommends a size range of 0-20 without some tweaking of size breaks but I omit that discussion as well in the interests of brevity.]

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