They seem to be close to full size when they start laying, they grow just slightly after that but not a lot. I have not weighed mine yet, I would like to though just to see. I have two hens that lay bigger eggs compared to the others, but they started first so maybe the others will catch up! And the shorter days kind of messed up their laying. Boy from June to end of September though they laid every single day without fail, now that I have the lights on them they are laying but not like they were, out of 5 hens I am getting 3-4 eggs a day, 3 most days. Don't you love their little faces? Their eyes when they look at you, looks like a lot is going on in their little heads
ETA: Oh! If you are asking how big the eggs get, not the hens...the eggs are a little bigger than a quarter most of the time now.
where do you live I am going to hatch some out in the spring but I didn't know where to get eggs. And what kind are they