That is hard to say because it does depend on the genetics of the bird. Most of my pullets are over 5# before they reach laying age, and some over 6#. Not all breeding lines are the same, so you can't really determine age by weight, necessarily. There are other things to look at though. Spread the wings and observe the feathers. If the bird is still growing new feathers in, it has not reached point of lay yet. You can tell old feathers from new ones coming in by the color, older ones are generally more faded, and the new ones should be wider and rounder than the juvie feathers. Then look at the color of the comb and wattles. A pullet who is coming into lay will become bright red in those areas. You can also feel the spread of the pubic bones ( the pointy bones when you feel from underneath and toward the back, almost like pincher shaped). When a pullet is coming into lay, the spread of the pubic bones should be about 2 fingers width at the gap. Also, a pullet or hen may start squatting as you reach for them when they come close to laying.What is the average weight for an adult hen? I am trying to figure out how old my bird is (see above pics of Molly) she is just over 4.5 lbs and has not laid any eggs for me.
You have to consider that this is the time of year that the days are very short. Unless you are providing extra light to them, most hens are not laying right now. I have well over 100 hens, and I get about 12 eggs a day. It is increasing now, but I also provide extra light on a timer to trick them into laying sooner than they would if I did not give them the extra light. Usually about early to mid February is when I start seeing eggs coming more in the birds I don't have lights on.
I hope this helps.