The imperial system of measure has a reputation for being unwieldy and complicated -usually deservedly- in all respects save one, that of drafting for the human body. While I can’t prove it, I think that it was precisely due to the particular suitability of inches in drafting for human bodies that are what made the imperial system so prevalent. While the system isn’t infallible, it can be a great rule of thumb for troubleshooting. In the forum we’d been discussing whether one’s instructor was using a good method. Said instructor was not grading for length in the neckline but was adding 1/4 to the armhole length and then again, nothing from armsyce (armpit) to the waist so it was easy for graders to see, without having a pattern for comparison, that this wasn’t the best way to go about it.
Most adult human bodies can be broken into eight head heights. Off to the right is an illustration from the Art of Drawing the Human Body.
Using this sketch, it is apparent that for every 1″ in height increase (or decrease if that applies), the pattern is lengthened according to these fixed points. For example, a cropped waist length top would grow 1/8th from nape to armpit and another 1/8th to the waist -and in precisely these locations. It wouldn’t do to add the 1/4″ of total length to just one area but must be spread according to the breakdown of dimensions of human height. Another example is a pair of shorts. Shorts would grow a total of 1/4″ in length with half going from waist to hip and another 1/8th from hip to mid thigh. Obviously styles will vary but this is a simple way you can check a pattern grade for people who are height and weight proportionate in that the patterns should grow commensurate to these guidelines.
In other words, to check a grade, you can’t compare over all length of two sizes relative to each other. First you have to line up the shoulder at the neckline to see the rate of grow to just the arm pit. Then you’d reposition the pieces to match at the arm pit to check the percentage of grow of each to the waist.
Last are two caveats. The first is, this applies to adults; children are “morphing” as they mature. Here is an illustration from pg. 170 of my book (right). An infant’s body is broken into fourths meaning one head length is one quarter of their total body length. Their trunks are disproportionately long, about half their total height with total leg length being about the same length as their heads.
The second caveat is that this applies to people who are height and weight proportionate. As people get heavier, the distance from point to point cannot be determined by strict x-y cartesian coordinates with a length caliper but are more accurately triangulated, “growing” disproportionately to the standard discernible pattern. This applies regardless of height as it is dependent upon girth. Moreover, as people gain weight, parts of their bodies will become disproportionate to each other which is why grading for plus sizes is a challenge.
Anyway, I just thought you’d appreciate a down and dirty method of comparing length grades if you have any doubts about the results you’ve either rendered or hired out.
I collect archaic mensuration depictions among other weird things. I don’t think I’ll ever have cause to publish this illustration below in another context but I think it’s fun. It’s from an ancient Egyptian text and even subtracting the overly elaborate headdress from total divisible height, doesn’t break down according to any scale we use today except perhaps one. It roughly approximates the scale of centimeters as expressed in terms of inches. I’m probably not saying that right (1″ =2.54cm) but I’ll have my math guy correct my oversight this evening.