i believe the difference in sizing only lays with the cup a woman who has a band size of 30 in the U.S. is the same as a woman who has a band size of 30 in the U.K. its the same cup sizes between UK and AUS the difference lies here, UK, AUS and US all go up to a DD, but the next size in the US is a DDD then a G as if DD is also an E and DDD is an F whereas in the UK and AUS DD and E are both two completely different sizes. So a woman whose a 32DDD in the US is the same as a woman who is a 32E in the UK
