Yeah, around three months after they start laying for egg size to stabilize. Egg size is determined by breed and can be different from hatchery to hatchery.
Egg size of each chicken of the same age and breed can be different.
To get the largest eggs from chickens, lots of fresh clean water. Eggs are mostly water.
Water should be easily accessible. I have water in the raised coop, under the coop and in the pen.
Also a higher Protein 18% feed in my experience produces a slightly larger egg, about one size up. I was feeding a 18% layers feed till 15 months old when I switched to a 16% layers feed and egg size on average dropped one size and went back up when I switched back to 18%.
Also my Golden Comets started to feather pick when I switched to 16% feed. Stopped about a month after I switched back.
I wouldn't go much above 20% Protein to increase egg size. A larger egg could cause laying problems. I lost a Golden Comet at 23 months to egg bound. She always laid eggs over 2 1/2 oz - 71 grams.
.GC
Egg size of each chicken of the same age and breed can be different.
To get the largest eggs from chickens, lots of fresh clean water. Eggs are mostly water.
Water should be easily accessible. I have water in the raised coop, under the coop and in the pen.
Also a higher Protein 18% feed in my experience produces a slightly larger egg, about one size up. I was feeding a 18% layers feed till 15 months old when I switched to a 16% layers feed and egg size on average dropped one size and went back up when I switched back to 18%.
Also my Golden Comets started to feather pick when I switched to 16% feed. Stopped about a month after I switched back.
I wouldn't go much above 20% Protein to increase egg size. A larger egg could cause laying problems. I lost a Golden Comet at 23 months to egg bound. She always laid eggs over 2 1/2 oz - 71 grams.
.GC
now the 92 gram double Yolker I just got ? That went into Saturday sourdough waffles 
