Note that many Australian and European clothing merchants have adopted the U.S. systems.

Also note that some suppliers have their own special sizing systems.

The system used in North America and the U.K. is not standardised, and there are large variations between manufacturers. Europe has a number of systems, with the EU system (based on the French system) becoming the standard.

Bra Band Size

Methods of calculating this vary a little, but the most common (for U.K. and North America) is the following: Measure around the torso just below the bust (in inches). If the measurement is an odd number, then add five inches to obtain the bra band size. If the measurement is an even number, then add four inches. For example, if the under-bust measurement was either 45 or 46 inches, then your bra size would be 50 inches.

Some makers recommend measuring above the bust, just below armpits, and taking this size (in inches) as the bra band size.

When measuring, the tape-measure should be kept level with the floor (with you standing up straight), and so it is better to have an assistant to help measure accurately (or get professionally measured). It should also be done when wearing a bra.

To confuse matters, some makers don't follow the above method for their larger sizes. For example, Aviana (an excellent brand from feedback I've heard) follow the "add 4 or 5 inches" rule for under-bust measurements up to 37 inches. For larger sizes, one has to add slightly less. E.g. If the measurement under the bust is 39 to 41", then band size is 42. Or for 42 to 44", the band is 44. 45 to 46" corresponds with a 46 band size for Aviana's sizing.

For European bra band sizing, measure under the bust (unterbrustweite/dessous de poitrine) in centimetres. For many countries outside France (including Russia, Sweden, Switzerland and Germany) this measurement gives the bra size. For France and standard EU sizing, add 15cm to this measurement (dessous de poitrine + 15cm) to obtain the bra size.

Problems for extra large ladies

For very large ladies, the above measuring system may prove unreliable for getting a good fit, even if measured professionally. The problem is that parts of your sides or back may be quite soft, and the bra band will sink in to some extent. But it is hard to know how tightly to hold the tape-measure, and there is a tendency to come up with a band measurement too large.

The solution is to experiment to find what size does fit. It is common for well-endowed ladies to wear a band size too large combined with a cup size too small. The shoulder straps are not there to support weight (the weight is taken by the band acting as a cantilever), and so they should not be digging in. If they are, it's possible that the band size is too large. A careful check of the cup fit should make it obvious if they are too small. Try a few cut-priced bras to establish the best fit, but keep in mind that sizing varies between makers as shown in tables on this page (see below). Underwired bras might be too uncomfortable for some ladies, and sadly, it is harder to find attractive wire-free bras (or ones that can be worn with a low neckline).

Cup Size

Measure your bust around its fullest part while wearing a bra. Subtract your bra band size from your bust measurement and then find the cup size from a bra size table, such as the one shown below. This is where manufacturers vary considerably, more so at larger cup sizes.