A problem with sizing studies

Tonya writes:

My target customer is taller than average, 5’6″ to 5’10” and I already know from research that I want my clothing to be cut with more room in the hip area than other manufacturers are using. I’ve gotten measurements from about 10 sources of plus-size clothing including Lane Bryant, Avenue, Jessica London Catalog, Ellen Tracy, Size Appeal, Torrid, Elizabth, etc. My latest bit of info came when I bought the ASTM 6960 plus-size standards.

My issue is related to fitting the bodice. [For my sample size] if I were to make a dress from a commercial pattern size 22 (44″ bust), it would be too small. But, if I make a 30W (52″ bust) it fits like a potato sack. Good plus-size clothing MUST fit properly in the bodice area so I want to draft patterns that will take into account, differences between chest and bust measurements. My plan was to analyze the chest/bust differences to see what the average cup size is for plus-sizes (C,D,DD) and draft patterns based on that instead of the normal B cup that I think most others use. To my surprise, the ASTM numbers don’t include a chest girth measurement, only the bust girth. Since you’re part of the organization I said, “Self, Kathleen will be able to tell me if there’s another set of measures on the 6960 that will give me the chest girth.” What I’m hoping is that I can take the back width and the front chest width and somehow get a chest girth measurement.

You have several things going on here. First, I can tell you the average cup size is a C, however, I don’t have any data on average cup size of plus size consumers. I don’t know that anybody does. Before I forget, if you are interested in any of the ASTM sizing related documents mentioned here, read my previous entry How to get sizing and grading standards.

Unfortunately, you are correct in that the dimensions listed in D-6960 do not include “chest girth”. I put that in quotation marks because technically, according to D-5219 (Standard Terminology Relating to Body Dimensions for Apparel Sizing), this measure is called upper chest girth. I know what you mean but the committee is very particular about this sort of thing. Again unfortunately, you cannot take the back width, the front width and get a chest girth measurement -and you couldn’t be more dismayed than I am about the matter. There’s a big disconnect between measures that are defined, and measures that are taken. Still other measures are taken and for the life of me, I can’t see that they are of any utility to anyone other than those stubbornly perseverating on the state of human anthropometry -but certainly little to nothing of value in application. We certainly can’t use them for drafting (there is a reason I joined the committee). The difficulty you cite is precisely the conflict I have with how sizing measures are taken. While I certainly haven’t surveyed the committee for their opinions on the matter, I can only think they presume the upper girth of the bodice can be readily shaped based on measures extrapolated from other areas such as shoulder and arc measures.

Regarding the back and front girth measures, these are called arc measures and they don’t encompass the circumference of the body. Still, these aren’t the only data sets available. For a time, I was corresponding with Kathleen Robinette, a biomechanics engineer at Wright Patterson Air Force Base who was working on standardizing the sizes of women’s naval uniforms. The set of reports (two booklets) she put out are quite useful even though the date of release is December 91. Since her research (an “in-house” survey of US naval women) wasn’t affiliated with ASTM, she was free to use measures she determined were useful. Of these was a measure described as chest circumference at scye; this is the measure that concerns you. Her data set (the survey taken) goes up to a size 22 (nearly 44″). The second booklet describes the dimensions of sizes that would be appropriate for uniforms. Those only go up to a size 18 but since the basis of her work is so sound, I’d think you could readily grade it from there. Another interesting factoid of her research is that she bothered to document women’s sizing dimensions by race.

If you want to know more about this project, google Sizing evaluation of navy women’s uniforms (item ADA249782). I guarantee you’ll find enough to keep you busy all week. You can also purchase the study, $22.95 for the download. If you want my opinion on the matter, I’d buy this one and pass on the second (below). Sick twisted individual that I am, I enjoy the results of this piece of work, it’s very useful for apparel applications. For the study, she analyzed the fit of several articles of clothing (blouse, overcoat, skirt, dress uniform -a tailored jacket) and collected anecdotal information from respondents regarding their satisfaction with apparel. The latter is usually absent from most sizing surveys. Lastly, the work includes charts and graphs, an array sufficient to warm the hearts and minds of the most ardent of data addicts.

You can also purchase the Development of sizing systems for navy women’s uniforms (item ADA232851) but it only seems to be available in microfiche. Maybe this would be available at a university library? If you were only going to buy one of these two, I’d suggest the former.

I close with the the abstract of the Sizing evaluation of navy women’s uniforms:

Abstract : Body dimensions relevant to the size and fit of Navy women’s uniform clothing were measured on a representative sample of 906 Naval officers and enlisted women. six commonly-worn items of uniform clothing were tried on each subject to find the size of best fit. Subsequent statistical analysis was undertaken to determine which body dimensions and which values of these dimensions beat predicted the size of best fit. The resulting information was used to develop sizing charts for use in catalogues from which Navy women order clothing. The reliability of the charts was tested on an additional sample of 170 women. Success in predicting correct sizes from the charts varied from 87% to 49% depending on the garment. Use of the charts resulted in 90% to 100% correct predictions within one size of best fit for all garments. A number Of sizing and design problems in the garments were revealed during the course of this study. These became the basis for a companion study (Robinette, et al 1990) in which new sizing programs for Navy women’s clothing were developed. Anthropometry, Navy, Best Fit, Sizing, Clothing, Women, Mail-order.

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  1. Jennifer says:

    Could one extrapolate the data from the EN 13402 data?
    Hopefully you can follow my train of thought.
    Though this sizing data does not have “underbust girth” measurement connected to size range it does have “underbust girth” measurement ranges and give a numeric difference for cup sizes
    So if I was working on size 22 as my base I would probably use the 122cm/106cm/127cm bust/waist/hip chart converting to imperial 48″/41.75″/50″. A “D Cup” is list as 18-20 cm or 7 -7/8″ difference. This would then make a 41 underbust girth
    I agree that plus size women over a size 20 have a larger average cup size than “average?” sized women

  2. Tonya says:

    Hmmm? I do follow your logic and I could do that because I do have the cup size numbers. I’d never thought about doing it that way but it would work, at least to get me started. I can adjust as I get more people to try on the garments.

  3. Jennifer says:

    Here is the EN data on Wikipedia.

    I was also note that for plus-size bras the “how to determine your bras size” rule of take your rib cage add 5 or 4″ thing does not hold as true I have found.
    If I used that method of determining my bras I be were and 46 D cup, I wear a 42 G/H depending on the model.
    The best fit chart I have found for plus size bras is from Avian. (though I were Primadonna bras).
    Here is the size chart http://www.avianabras.com/fit_chart.htm
    I hope that also helps

  4. Barry Foxman says:

    Its difficult to say how much Tonya know’s, as the first thing I did was to look up the latest ASTM Women’s sizes and I don’t understand where
    she is getting her size 22 with a 44″ Bust info. The ASTM D 6960 Size 22 Bust recommends 47 1/2″ (Which is Plus 3 1/2″ over what she say’s and
    makes sense why her size 22 is too small.)
    In addition she discusses Front to Back chest widths, which a good patternmaker can gain info from the 6960 Study, such as;
    Trunk Length (Total Vertical)
    Bust point to bust point
    Neck to bust point
    Across back shoulder
    Back width and
    Across front chest.
    The average Height for the ASTM 6960 is 5′ 6″. In that case she needs a Tall spec.

    I measured one of my forms and there is almost a 5″ difference from the front bust
    which is larger then the back.

    If there is anyway I can be of further help, please let me know.
    Barry Foxman
    President, The Fitlogic Institute

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