I decided to post this one in English too. Don’t take me too seriously, I’m not a professional survey person and I suck at statistical stuff. Briefly: A couple of weeks ago I made a little survey, asking body measurements and perceived bra and clothing size from Finnish speaking internet users. I got over 300 entries, and only had to discard a handful (because of typos etc. that couldn’t be fixed). There are some interesting outliers that may be incorrect, but the measurements are plausible, so I didn’t remove them. So the final sample size was 307.
Most respondents were between ages of 20 and 39, living in Helsinki Metropolitan area or other large cities in Finland. Their height distributions seems to be similar to the heights of women of similar age in a recent large study on Finnish population (FINRISKI 2012) and their BMI is slightly higher, but not much so. So at least it looks like the respondents are a decent enough sample of Finnish female young adults that live in cities.
I asked the respondents to measure take their bust measurement standing up, wearing a well fitting, thin bra. The tape should be loose but stay in place. I asked for the underbust measurement to be taken tightly, exhaling.
The bust measurement varied from 75 cm (29.5 in) to 146 cm (57.5 in), with an average of 100 cm (39.5 in) and a median of 98 cm (38.5). The underbust measurement varied from 63 cm (25 in) to 115 cm (45.5 in), with an average of 80 cm (31.5 in) and a median of 79 cm (31 in). You can see the distribution of the measurements below.
The European band and cup sizes were calculated by the EN 13402 standard. The band size is the closest number to the underbust measurement, by increments of 5 cm. The band sizes ranged from 65 to 115 (30-50 in UK sizes).
The cup size depends on the difference between bust measurement and band size. You can see that according to the standard, many respondents have a cup size that is smaller than AA. That is because their bust measurement is less than 10 cm bigger than their band size. Cup size uses 2 cm increments, so A cup is 10-12 cm difference to band size, B cup 12-14 cm etc. The largest calculated cup size was U.
UK sizes were calculated by converting the measurements to inches and rounding the underbust measurement to closest even number. The ’plus 4’ method, where 4 inches are added to the underbust measurement to get the band size, gave the following results. Band sizes ranged from 28 to 50 (60-115 in EU sizes). There is not much difference to the EN standard.
The cup sizes were calculated from the difference of bust measurement (rounded to closest integer) and band size. Negative number means AA, 0 inch difference is A cup, 1 inch is B cup etc. The largest cup size was L. The UK method uses 1 inch (2.54 cm) increments vs. the 2 cm increments in the EN standard, so fewer cup sizes cover a larger range of measurements.
The plus 4 method rarely gives the best results for women with large busts. The EN standard also tends to give a band size that is too loose. They both originate from the time before Lycra, and were useful because they gave some breathing room with the not so elastic fabrics. Recently a popular approach has been to use the underbust measurement in inches directly as the band size. On my survey, this ’plus 0’ method resulted in band sizes ranging from 24 to 46 (50-105 in EU sizes).
The cup sizes were once again calculated from the difference of bust measurement to band size, with one inch increments. They ranged from B to N.
The most common bra size in both the EN standard and UK plus 4 method was 75D (or 34D), with 80D (36D) coming in second. The percentages were 4.9 % and 3.6 % respectively, with the EN standard calculations. I didn’t calculate the UK +4 percentages (sorry!) but they were probably on a tiny bit bigger (due to the slightly larger increment). I believe the results are similar to many of the ”most popular sizes” reports from various sources.
With the UK +4 method the most common bra sizes were 65FF or 30FF (5.5 %) and 70FF or 32FF (5.2 %).
Now a bit more about the size distributions. With the EN standard, a shop could cater to about 51 % of the respondents by carrying the EU sizes 32-38 A-F. That’s 24 sizes in total. But doubling the size range to 48 sizes won’t get you to 100 % coverage, but just below 80 %. For a coverage of 90 % you would need about 60 sizes. And yet the 10 % that is left out is the 10 % that need supportive bras the most.
With the UK methods you get better coverage because the cup size increments are a bit larger. With just the 24 bra sizes you’d cater to about 62 % of the respondents. The sizes are, according to the +0 method, 28-34 D-GG (60-75 in EU band sizes). It’s possible that this is a range where the +0 method gives good results. A similar size range with the +4 method, 32-38 A-E (70-75 in EU band sizes) covers about 59 % of the respondents.
The data’s not fully explored yet and there’s a lot of stuff I could cover. What would you like to know about?