Alphabet Sizing vs BCD
Updated: Jan 14
Why the Bottom Cup Depth method is the most accurate way to measure your cup size
When you walk into the lingerie section to buy a bra, you make your selection based on your cup size and your band size -- you might be a 34B or a 40G, for example. These cup sizes are referred to as the "ABCD" or alphabet method, which has been around since Warner issued the Alphabet Bra in 1937. Alphabet cup sizing is generally defined as the difference between your bust measurement and your rib cage measurement size. It's a simple system, but it has significant drawbacks.
Problems with Alphabet Cup Sizing
First, manufacturers have never agreed on a standard, which means you can be a different cup size depending on which line of bras you wear. There's also the issue of assigning letters to the different cup sizes. In one line, you might have a C, D, DD, DDD, and G (and so on). In another, you might have C, D, DD, E, F, G. Try shopping in another country and it will be completely different again!
The first "alphabet bra" came out in 1937 in only four sizes--A, B, C and D.
Adding to the confusion is a lack of standardization around band sizes--retail manufacturers use the rib cage measurement PLUS a "magic number" to get to the size on the label, and each manufacturer has a different magic number! If your band size is 36, your actual rib cage might be 32 inches.
If all of this wasn't enough, manufacturers sell consumers on the idea of "sister sizing", arguing that bras with different band and cup combinations actually have the same volume--for example, they say that a 30D is the same as a 32C, a 34D, and so on. This is a cost-savings measure since it dramatically reduces the range of sizes they actually have to produce.
Confused? It's not just you. It simply isn't a good system. Oprah said that up to eighty percent of women wear the wrong size, but as we've just seen, this stat is more complicated than it seems.
The BCD Method
The Bottom Cup Depth method, created by bra designer Beverly Johnson (and used in her Pin Up Girls line of patterns) is much simpler and more accurate. It is based on one simple measurement--the distance between the inframammary fold (at the base of the breast) and the apex (the highest point, or the place where your nipple would be in a perfect world). So, if you're a 6.0 BCD, there's six inches between the inframammary fold an the apex. And your band size? Well, it's your rib cage measurement with no "magic number" added. Done. Easy peasy.
There are "conversion" charts that can translate your approximate BCD based on the the retail cup size that you've been wearing, but this is just the starting point for fittings. Using "tester" bras, which have cups with standardized BCDs, I can help you find your true size in a properly fitted custom bra.