Male or female? If it's a barred rock, you are supposed to be able to tell the first day.
Females: small, distinct head spot and dark(er) wash down the front of the legs.
Males: large/blurry head spot. Legs not as dark.
Overall males will be much lighter than females. I currently have a chick that seems to be splitting the difference. Small non-distinct headspot and so-so with the black wash. Her feathers are coming in and they look more black than white to me, but I have seen pics of some with the same ratio that turned out to be boys. I think it will be a roo that looks enough like a girl to keep me guessing. I feel for you.
Females: small, distinct head spot and dark(er) wash down the front of the legs.
Males: large/blurry head spot. Legs not as dark.
Overall males will be much lighter than females. I currently have a chick that seems to be splitting the difference. Small non-distinct headspot and so-so with the black wash. Her feathers are coming in and they look more black than white to me, but I have seen pics of some with the same ratio that turned out to be boys. I think it will be a roo that looks enough like a girl to keep me guessing. I feel for you.