The Shoulder to Shoulder width is crucial for making wide necklines that don’t fall off the shoulder. It is also crucial for spacing the straps on corsets and bodices so that they stay on the shoulder and you don’t have to fuss with them all day.
The Neck to Waist Length is to the back of the body what the Nape to Waist Length is to the front: the basic measurement of the back of the body. If you’re hoping to make a fitted garment work in back, the Neck to Waist and Neck to Shoulder Lengths are what you need.
The Nape to Waist Length measurement is, basically, the length of material needed to cover the front of the body from the bottom of the neck down to the waist. It is a crucial to take this measurement correctly if one has any hope of drafting a bodice that fits correctly over the bust without riding up at the waist. Nape to Bustline Length tells us where the bust line is situated on the torso, and is also crucial to drafting patterns.
The Neck to Shoulder Length is crucial to making shifts, jackets, bodices, doublets, and basically any other garment with a fitted shoulder and/or a sleeve that sits at the point of the shoulder. If your Neck to Shoulder Length is off, your finished garments will always look droopy-in-the-shoulder (too long) or have that entirely unflattering Ack!-my-sleeves-are-attacking-my-head effect (too short). The first case, the drop shoulder, comes in and out of fashion, but the second is pretty universally regarded as a bad idea….
The Neck measurement is used in fitting any garment or accessory meant to sit closely around, or upon, the neck: collared shirts, gorgets, doublets, chokers, and early ruffs, to name a few.
Ankle measurements are useful for knitting custom socks (why, don’t you?), making jewelry (specifically anklets), and fitting big-poofy-gathered-at-the-ankle style pants (clowns, harem pants, etc).
Calf measurements are used for tall boots, tall spats, and jodhpurs and fitted crop pants.
Knee measurements are used any time a garment fits close around the knee. I mostly seem to use them for making gathered bloomers and knickers.
Thighs happen. I’ve personally always found that a bit disappointing, especially when I try to find pants that fit. If you’re making a bifurcated nether-garment of any sort, and you want it to fit over your thighs, it’s helpful to have a proper measurement. This measurement is also used in many men’s short-pants throughout history (canions, slops, etc).
The Inseam is the classic measurement used by tailors everywhere to hem a pant. It runs along the inside of the leg, from the crotch to the welt of the shoe, and has been the source of a lot of humor about pant fittings. Because of that, many of us use the, ahem, “less personal” Outseam measurement….