Different countries use different bra sizing methods, I'm sure this is just to confuse us even more!
The UK and USA are very similar using the Imperial system with a letter cup size.....but once you get towards the larger cup sizes things change. See the comparison chart below.
In most European countries the sizing is done in Metric with a letter cup size, but again this is not the same for all countries in Europe. Italy uses a different system again!!
Australia use a totally different system which is based on the dress sizing charts.
Hopefully the charts will help you out when purchasing lingerie online from different countries.
Remember that if your bra is feeling a little uncomfortable, try on a bra +1 or -1 cup size and band size, it may help you find the right size for YOU.