BREED TYPE AND THE WEIGHT OF THE CHICKEN ARE OTHER FACTORS WHICH CAN AFFECT EGG SIZE. GENERALLY SPEAKING, THE OLDER THE CHICKEN, THE LARGER THE EGG. As the yolk travels through the oviduct, it is continually rotating, which twists structural fibres into rope-like strands that anchor the yolk in the thick egg white. This is why the yolk is always at the centre when you crack an egg open. DID YOU KNOW? EGG SIZE In Australia, egg sizes are graded on the basis of their weight1 as follows: Size category Weight (grams) Medium 41.7 – 49.9 Large 50.0g – 58.2g Extra large 58.3g – 66.6g Jumbo 66.7 – 71.6g Extra jumbo 71.7+ 1 Source; Australian Egg Corporation Limited Labelling Guidelines THE CHOOK BOOK | 11