I am smaller than your average bear. Both shorter than average (for a Western man -- by around one standard deviation), and also near the low end of the "normal" BMI for my height as a result of being on the thin side of average. Together these cause all sorts of problems finding clothes that will fit well, particularly since I dislike wearing excessively baggy clothes (and most easily available clothes are excessively baggy on me!). This post is my record of sizes of clothing items which I have found will fit; I'll probably update it periodically as new information comes to hand.
It is relatively uncommon to find clothes in my size available at discounted prices (except perhaps store-wide sales), as they are normally sold out prior to being discounted (where they are stocked at all). At minimum the range of styles will be sufficiently reduced that it is better to look for items in my size first before deciding if any styles appeal, than to look at the styles first. Quite a few stores don't even stock any items in my size, at least in Wellington. (In some cases the same chains in larger cities, eg, in Australia, may stock my size, and in those cases it may be possible to special order the items into Wellington. But even in larger Australian cities many stores do not stock anything close to my size.)
Aside from the size problems, finding things in a style I want to wear is also difficult: I prefer items in plain, solid colours, typically relatively bold colours (particularly when worn to contrast each other). For years most of the stores have been filled with patterned items that I would not choose to wear. And often the colours offered in men's clothes are very muted and unappealing. I also like my clothes to be functional (eg, full zip jackets with pockets to carry things; trousers with pockets that open to the top -- like jeans -- rather than to the side where things put in the pockets want to fall out). Sadly that sort of functionality often seems to be an after thought (particularly in women's styles).
Summary of sizes
From top to toe:
Hats: USA size 7, UK size 6 7/8ths, French size 4 1/2 (based on conversion charts, see also Wikipedia on hat sizes; my head size approximately 55.5cm, which is about 21 and 7/8 inches). Medium (57cm) is usually the best fit, depending on the style (but can sometimes be a little loose); small (55cm) is generally a bit too tight to be comfortable. (And 56cm should be "just right" if actually available.)
Dress shirts: Men's "XS" (extra small), preferably slim fit. Tarocash and YD regularly stock XS, but they can sell out quickly of that size so it is relatively uncommon they end up on sale (their men's XXS is usually too small across the shoulders; men's S is too big). Hallensteins will stock XS in some styles (eg, plain business shirt, which are regularly on two-for-$N specials).
36cm neck, in a slim fit if worn open necked. 37cm neck in a (super?) slim fit would be better if worn buttoned up with a tie (and the poor fit elsewhere hidden by a jacket). That equates to a 14 to 14.5 inch neck, for USA sizing. Any "relaxed fit" styles will be massively too big; "tailored fit" is generally a looser fit too. (Women's size 10 shirts/blouses usually have too much bust, and/or plunging neck line, tailored in to fit my body shape well.)
Casual shirts: Icebreaker (see below). Polo shirts in women's size 10 (M) will often work and are widely stocked (the sleeves can be rather short though, and they may be narrow across the back, so a stretch fit helps). Particularly slim fitting men's small in a stretch fabric sometimes works. ("XS" doesn't usually exist for men's T-shirts, but may possibly exist in polo shirts in large cities. I haven't found any good T-shirt solution, as women's styles are normally too scoop necked for my body shape, and men's styles are too big. But since T-shirts normally have prints on them I do not want to wear, it is possibly not a big loss.)
Icebreaker: women's "M" (medium) for tops, in a "crewe" style (ie without the scoop neck). I literally own a drawer full of them, and it is one of the few things I will buy without trying it on, if it is discounted (Icebreaker only allows discounts a couple of times a year, and sadly the women's "M" is often one of the first to sell out). Women's "S" (small) for leggings (a tight fit, but the "M" is baggy around the hips/buttocks, and fortunately the Icebreaker stretches). All the men's items are too big, except perhaps the men's small overcoats (which are loose, but that's useful in an overcoat).
Dress jackets: 88cm (34 inch) chest. 92cm (36 inch) chest is usually a bit too big, and not worth considering unless the price is amazing (eg, second hand or deep discount); anything larger is way too big. 88cm jackets/suits do turn up periodically, even on good discounts, and are probably at least as common remaindered as on regular racks. They can probably be special ordered more easily than found in store, but that would involve paying full retail, which is usually insanely expensive in New Zealand.
Casual/outdoor jackets: women's size 10 or 8 (NZ) or size 8 or 6 (USA) seems to work best (and the range of colours is better too) (Men's "S" -- small -- is too big, and "XS" basically doesn't exist for casual jackets.) Many styles are a little too tight across the shoulders, so a style with a bit of stretch is usually best, and carefully trying them on is always required (fortunately it's easy to try jackets on). The arms may also be a little short, but usually not so much to be unworkable.
Gloves: Women's medium will usually work, or sometimes men's small.
Underwear: Men's small, usually "75-80cm", is often okay when new, but gets progressively loose as it wears in. Anything that doesn't at least mention 75cm is probably too big, and sadly 80cm seems to becoming the new "men's small" for many things. Davenport bodyshorts seem to be a pretty good fit. (It'd be nice to find something a little smaller, but it's not obvious how; there is no men's XS for underwear, and women's styles are built for a very different body shape. Boys size 14 (boys XL) might work (usually quoted at around 72cm), but may also be a little tight and the range of styles is much reduced.)
Trousers: 28 inch (72cm) waist, which often means US-originated brands and a limited choice of styles. 74-76cm (29/30 inch) waist may be workable in a tightly cut style. (Like most things, the unit of measurement of the country of origin is usually more accurate than the converted unit, and 28-29 inch waist is the right size. Annoyingly sometimes even 80cm waist will be shelved as if it is 30 inch waist -- 80 cm is nearly 32 inches! -- so double checking is required.) Avoid pleated front trousers, they are too baggy.
Levi 504 jeans in 30 inch waist are rather loose, and not available any smaller; Levi 501 in 28 inch waist fit reasonably well, but are button fly; Levi 505 in 28 inch waist are okay. Probably need to try other jeans more extensively. Dress trousers are relatively easy to find in 77cm waist, and good ones are often designed to be easily taken in (or let out) a little. Stock of casual trousers, other than jeans, can be pretty variable. (And as with other clothes, typically these do not exist in the sales piles. Of note, many of the dress trousers seem to be massively too long in the leg, but I guess one could have someone take them up for some unknown additional cost. A 31 inch -- 79cm -- leg is about right, and 32 inch will work; 30 inch leg is a bit short.)
Shoes:
- UK size 7.5 or 8 (7 is usually too small)
- USA men's size 8.5 or 9 (8 is usually too small; need about 10 in USA women's sizing, but they may be too narrow)
- 41 (+/- 1) in the European system based on left foot length of 26cm, and right foot length of 25.5cm; exact size depends on wiggle room beyond the last needed by the shoe design. (See shoe sizing background detail below.) I should always try the left foot first, as the right foot will often work in a shoe half a size smaller than is really practical for the left foot (half size smaller is around 4 mm, roughly the difference in my foot size left to right).
Hi-Tec and Hush Puppies seem to generally fit well.
Socks: Men's size 7-10 (units unspecified!) socks will usually fit fine. Stretch material for the win. (It's one of the few items I feel confident just buying off the rack.)
Background detail
For future reference, some historical sizing reference material that I found while researching it. (I may add to this section over time too, if I find anything else particularly relevant.)
Shoes
In the previous decade or so I have found it difficult to find shoes that fit well, in a style that I wanted to wear (and at a price I was willing to pay, given they usually didn't fit too well). Too often "fit well" was the thing sacrificed. Recently I discovered enough detail about common shoe sizing systems that means the search process should be considerably more efficient (even though I am near the bottom end of what is regularly stocked).
In New Zealand/Australia shoes are usually sold sized by one or more of the UK system, the USA system, or sometimes the European system; usually depending on where the manufacturer is (or was originally) based (generally the primary system in the country of the manufacturer will be the most accurate, and the rest will be translations). Quite a few shoe brands will list all three sizes with varying (unstated) degrees of accuracy; and some will also list a length in centimetres (which I think is the length of the last -- see below).
In all three of the UK, USA, and European systems the shoes are sized based on the length of the last. The last is essentially the form used for making the shoe (historically the shoe was literally assembled around the last). It approximates the shape of the human foot (the precise shape of the last used will vary depending on the purpose of the shoe, and typical foot profiles in the country of origin, as well as between brands). This means that in all three systems, for most shoe styles, some "wiggle room" is required to allow the foot to flex while the shoe is in use (eg, walking) without getting crushed against all sides. Typically about 1.5cm to 2cm extra foot room is suggested (the Brannock device, for measuring feet to identify appropriate shoes, uses a formula suggesting 2/3rds of an inch, which is about 1.7cm).
The UK and USA systems both use the same underlying historical unit of measure, the barleycorn (featured on QI, and in a list of odd units of measure). The barleycorn is 1/3rd of an inch (just under 8.5mm), and has been in use in England and Wales at least since the 10th C. The key difference between the UK system and the USA system is the offset value used in the calculation, which differ by 1 (for men's shoes), so UK size 0 is USA size 1. (For women's shoes the difference is either 2 or 2.5, depending on which USA convention the manufacturer decided to follow, so you really have to try them on to find out; in the UK system women's sizes and men's sizes should be directly comparable -- but women's shoes will generally tend to be narrower than men's shoes across the board).
The European system is based on Paris Points, which is defined as 2/3rds of a cm (so about 6.7mm, approximately 1/4 inch -- apparently it is closer to a quarter with the historical French "inch" equivalent, which was slightly larger than the modern standardised Anglo-Saxon inch of 2.54cm). Unsurprisingly the European system is based on foot lengths in cm (the UK and USA systems are based on foot lengths in inches), but otherwise the approach is similar: add about 1.5cm of wiggle room, and then convert to Paris Points. (There's no offset used in the European system, so numbers in the 30s to 50s are common.)
Given a foot length of foot_len cm, and allowing 1.5 cm of "wiggle room", the resulting calculations then become:
UK: shoe size = 3 * ((foot_len + 1.5 cm) / 2.54) - 25
USA: men's shoe size = 3 * ((foot_len + 1.5 cm) / 2.54) - 24
USA: women's shoe size = 3 * ((foot_len + 1.5 cm) / 2.54) - 23 (or - 22.5)
European: 3 * (foot_len + 1.5 cm) / 2
For my (left) foot of 26cm (my right is 25.5cm) that works out to UK size 7.5, USA men's size 8.5 (women's size 9.5 or 10), and 41.25 European (Paris Points) -- although European shoes are normally only sold in full (or perhaps half) Paris Point sizes, so that's 41 or 41.5 (or maybe 42). Experience tells me anything smaller than that (eg, USA size 8) is just too tight to be practical on my left foot (even if it might work on my right foot). (Vibram Five Fingers, which are designed to be skin tight and flex with the skin, are probably the only exception; European size 40 may possibly work there.)
Like everything involving clothing, some approximation is required, especially when the difference between full and half sizes is about 3.5mm to 4mm (UK/USA). That difference is sufficiently small that it can be swamped by subtleties in the shape of the last, the style of the shoe, or the amount of wiggle room that is desired (eg, hiking shoes might need a little more wiggle room than dress shoes). But knowing that the most accurate sizing is likely to be the one of the country of origin of the manufacturer (and all the rest are likely to be approximate/rounded conversions) may speed up the search process.
For reference, some shoe size conversion charts (of varying accuracy; the formulas above seem more likely to be correct): dance shoes and men's shoes from New Zealand.
ETA 2013-05-19: Updated sizing information for casual jackets and trousers. Also worth reading: Levelling Up: Building a Cool Wardrobe, and Fashion for Nerds.