Roughly...very roughly(just so no one takes it as carved in stone)
When I first started I had to change them more often, but I got better at it.
But some birds grow at different rates....so Observe and Adjust.
Right out of the hatcher.
...and for those wondering, yes, I check them frequently and change out as needed.
https://www.backyardchickens.com/articles/leg-banding-with-zipties.68075/