The time it takes for a pullet to begin laying varies primarily on the breed and the time of year she was hatched. A hen will usually go ‘dormant’ in the coldest seasons. This means that chicks hatched in Fall or late summer will often hold off on laying until the following spring…
When a Hen Starts Laying:
Most hens will begin lay at between 4 and 8 months of age. However, each hen is different. Even hens of the same breed may not start their first laying season at exactly the same time.
Some breeds are slower to mature than others. Generally, the bigger, heavier breeds (Such as Cornish crosses, Wyandottes and Brahmas) start lay the latest and the lightest, smallest breeds (Like Leghorns, Egyptian-Fayoumis and Easter-Eggers) start lay the soonest. However, many dual purpose breeds that where bred for both meat and egg production (like Rhode Island Reds, Sex-Link Hybrids and Plymouth Rocks) begin laying on the early end of the spectrum (~6 months). Some lightweight, Ornamental (fancy) breeds, which are usually not bred for egg laying purposes may mature slowly (even many lightweight varieties). For this reason, many ornamental chickens, (like Polishes and Crevcouers) may not begin laying until 7-9 months.
Notes about expecting the first eggs
Something to take into account when expecting eggs from pullets is that when Pullets first begin laying, the size of the egg will be smaller than average. This is normal and to be expected. Over time, egg-size will gradually increase (with healthy chickens). Defective eggs are also to be expected when pullets begin to lay. Soft shelled eggs and misshapen eggs are also a normal occurrence in first year layers but not on a regular basis and should happen no more than once or twice.