Found this for Aussie sizing.
Australian buying an American shirt? Order a 1/2 size smaller than normal.
American buying an Australian shirt? Oder a 1/2 size larger than normal.
Australian Size = US Size
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XS, S = S
M, L = M
XL, XXL = L
3XL, 4XL = XL
5XL, 6XL = 2XL
7XL, 8XL = 3XL
How do you convert American shirt sizes to Australian shirt sizes