Akubra hats are adaptable, and will usually conform to differences in shaped heads with a little wearing, it is essential that the size be correct for your head.
NOTE: For in-between measurements use the next size up.
The Sheepskin inner band of the hat may shrink slightly with use. Do not expect a tight-fitting hat to 'loosen up'
In time, the hat will conform to your head shape. Initially, a slightly loose-fitting hat can be adjusted using folded tissue placed behind the inner band, then removed as the hat conforms to your head shape.