As the author of this blog and a seller of second hand menswear, I am frequently asked questions regarding the measurement and sizing of old garments. In the age of the internet, more clothing than ever is bought and sold sight unseen via places like ebay and online shops like my own. In the interest of a "Reader Questions" style post, here's a guide and explanation of how sizing works and how to use measurements to successfully shop for old clothes.
Most modern clothes are sized on a tag. These measurements can be anything as vague as "alpha sizing" (S,M,L,XL) or as specific as tailored sizing (42 Reg., for example). While helpful, these sizes are best used as a guide rather than a rigid fact. In truth, there is fluidity in such sizes, and different manufacturers or brands often use the same numbers on clothes which are not physically the same size. Add to that the fact that many older and vintage clothes are either missing these tags or were never sized that way in the first place, and things can get pretty confusing. While it's helpful to know about what "size" you are, it is infinitely more helpful to know your measurements, or even just the measurements of an article of clothing that fits well. The numbers on a measuring tape are marked out in inches (or centimeters if you live anywhere but here), and there is no arguing with them.
Most suit jackets and sport coats are sized by chest measurement and length. For example, I generally wear a 42 Regular. The number (42) refers to the circumference of the chest, in this case 42 inches, while "Regular" refers to the length of the jacket measured down the back. Generally speaking, there are five measurements to know on a tailored jacket. The chest can measured by laying a jacket flat and measuring from armpit to armpit, or "pit to pit" as you'll often read in online listing, then doubling. Bear in mind that is a differential to be considered, and few extra inches need to be left for freedom of movement. The jackets I have that I consider 42 chest measure between 22 and 23 inches across, or between 44-45 inches around. Shoulders are measured across the back from point to point. This can vary between makers and styles, but it can't be altered, so know what fits.A little variance is ok here. For example, I can wear anything from 18-19 inches in the shoulder. Length is usually listed as Short, Regular, and Long. While there is no hard rule about these lengths, I generally consider a "regular" to be about 31 inches from the bottom of the collar to the hem of the coat, short to be about 30, and long to be about 32. Again, the terms are subjective, but the numbers are not. Sleeve length is measured from shoulder to cuff, and sometimes a waist measurement will be given by measuring across the closed buttoning point. These can be helpful, but remember too that sleeve length and side seams are easily altered. A good seller will list how much cloth there is to accommodate these alterations, or at least be able to tell you should you ask.
Trousers are easier, with the most important measurement of course being at the waist. This is measured much the same way as the chest of a jacket, across the waistband, doubled, with room to move. For example, what I would consider a 36 waist would actually measure about 37 inches. Length is measured from the crotch to the hem down the seam. This is easily alterable in most cases and a good seller will tell how much extra cloth there is to make adjustments. If you're looking for trim or fuller cut trousers, it's helpful to know the leg opening and thigh measurement. A leg opening between 9 and 10 inches is fairly classic, with 8 inches being trim. 13-14 inches at the thigh is classic, less would be considered trim cut. If you like a trimmer look, trousers can often be tapered in a bit, but you'll need a good tailor, not just the local dry cleaner. Remember that honesty with oneself is important. You may like to say you wear a 34 waist when you really need 36. Vanity is a funny thing. It should motivate you to wear clothes that look good rather than squeeze into uncomfortable clothing that's too tight.
These things are not only helpful in the world of online shopping, but also in the physical realm. Take a measuring tape with you to the thrift store and ignore tagged sizing. If you see something you like, measure it and see how close it comes to the measurements taken from a well fitting garment you already have. With experience, you'll begin to see the relativity in tagged sizing. I personally own and wear trousers sized from 34 to 38 inches, and jackets ranging from 40 to 44 in tagged sizes, and yet they all fit. Know measurements, not your "sizes".
p.s. A Note on Blog Posts
You may have noticed that posting here has become less frequent, lately only happening once a week, usually on Saturday. As some of you may know, I have taken a writing job with the style blog at ehow.com. This job, paired with the running of both my online and brick and mortar shop, has made it difficult to keep posting here as frequently as I would like. Going forward, I will be working out a more regular posting schedule for the blog, likely twice a week. Until then keep checking in and bear with me. I truly appreciate your readership and will continue to offer the kind of content you've come to expect. Thank you.