When Do ISA Brown Chickens Start Laying?
ISA Brown pullets typically lay their first egg at 16–18 weeks old (3.7–4.1 months) — among the earliest-laying breeds.
- First egg window
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- pick a hatch date to see your timeline
What to expect from ISA Brown layers
| First egg | 16–18 weeks (3.7–4.1 months) |
| Egg color | brown |
| Eggs per year | ≈ 300–350 in the first laying year |
| Size class | standard |
A commercial hybrid bred purely for egg output — the earliest, heaviest layer most keepers will ever own. The trade-off is a shorter productive life than heritage breeds.
Why your ISA Brown might lay earlier or later
The 16–18 week window is typical, not guaranteed — individual hens vary, and hatchery strains of a breed often lay earlier than show-line birds bred for looks over production. The biggest wildcard is daylight: laying is triggered partly by day length, so a pullet reaching laying age in late fall commonly waits for the lengthening days of late winter, no matter what the calendar math says. Spring-hatched chicks usually run on schedule.
You'll know eggs are close when the comb and wattles flush red and the pullet starts squatting when you reach toward her — first eggs usually arrive within a week or two of the squat. Switch to layer feed around week 18 (or at the first egg), keep oyster shell available, and expect the first few eggs to be small or odd-shaped while her system calibrates. All normal, all edible.
Use the calculator above with your chicks' actual hatch date for the expected window, or compare all 30 breeds on the full First Egg Calculator.