Coop Lighting Calculator

Why winter lay drops off

Egg-laying is triggered by day length, not temperature. A hen's pineal gland responds to hours of light, and once natural daylight dips below roughly 14 hours a day — which happens through fall and winter across most of the US, UK, Canada, and Australia and New Zealand's winter — production slows or stops and hens often molt around the same time. That's not a problem to fix; it's the normal annual cycle for a flock with no added light. Supplemental lighting is a choice some keepers make to keep eggs coming through the dark months, not a requirement for a healthy flock.

In December, a coop at New York's latitude gets down to about 9.28 hours of natural daylight — well under the 14-16 hour range hens need for peak production. Enter your own area above to see your actual numbers, month by month.

How this works

The calculator computes your area's natural day length — sunrise to sunset — from your latitude and today's date, using the same astronomical model behind most sunrise/sunset calculators. It's cross-checked against official U.S. Naval Observatory sunrise/sunset times and matches within a couple of minutes, which is more precision than a coop light schedule needs. Pick the city closest to you, or enter your exact latitude — southern hemisphere keepers should enter it as negative, and the seasons flip correctly (December is high summer in Sydney, not winter).

If today's natural daylight is under 14 hours, the calculator shows how much supplemental light closes the gap. If you're already inside the 14-16 hour range, no light is needed — and if natural daylight is already above 16 hours (only relevant at high latitudes near the summer solstice), more light adds nothing: there's no evidence it increases production further, and hens still need a real dark period.

Add the light in the morning, before sunrise — not by extending it into the evening. Hens naturally head to roost as the sun goes down; a light left on past dark and then switched off abruptly can strand birds off the roost, since chickens have poor night vision and can pile up in a corner trying to find it. A light that comes on before dawn and goes off once the sun is up lets the flock still wind down with the real sunset, on its own schedule. Put it on an automatic timer — that's also how you avoid the trap of remembering a manual switch every evening and skipping nights, which does more harm to a laying schedule than skipping light altogether.

Ramp the change gradually rather than jumping straight to a full winter schedule — extension guidance caps it at about an hour of change per week in either direction, since a sudden jump stresses the flock. Keep the bulb low intensity: hens only need enough light to read a newspaper by at bird level, and one source we cite caps incandescent bulbs at 30-40 watts. A separate coverage rule sizes a 60-watt incandescent bulb (or a 9-watt LED equivalent) per 200 sq ft of coop and run — the two figures measure different things (a brightness ceiling vs. a coverage rule), so we show both rather than picking one.

A worked example

A keeper in the New York area checks in mid-December. Natural daylight is down to about 9.28 hours, well short of the 14-hour floor. The calculator shows roughly 4.72 hours of supplemental light needed. Rather than flipping a switch that night, they set a timer to turn the coop light on before sunrise, ramping the total up by about an hour a week until they reach the full addition — so by early January the flock is back on a full 14-hour day, still winding down naturally with the real sunset each evening.

Frequently asked questions

How many hours of light do laying hens need?

Extension guidance puts the target at 14-16 hours a day. Egg production drops off once natural daylight dips below about 14 hours, and there's no added benefit past 16 — a photoperiod that long doesn't stimulate more eggs and cuts into the dark period hens need.

Should I add light in the morning or evening?

Morning, before sunrise. Hens naturally head to roost as it gets dark, so a light that stays on into the evening and then cuts out abruptly can strand birds off the roost — they have poor night vision and can pile up in a corner. Adding light before dawn lets the flock still wind down with the real sunset.

What happens if I skip supplemental light in winter?

Nothing dangerous — it's a choice, not a welfare issue. Hens naturally slow or stop laying as days shorten and often molt around the same time; that's the normal cycle a flock without added light follows. Supplemental light just keeps production going through the months it would otherwise pause.

What kind of bulb should I use?

Low intensity is enough — extension guidance puts the minimum at about half a foot-candle, roughly bright enough to read a newspaper by at bird level. One source caps incandescent bulbs at 30-40 watts; another sizes a 60-watt incandescent (or a 9-watt LED equivalent) per 200 sq ft of coop and run. Either way, put it on a timer rather than relying on remembering to flip a switch.

Can I change the light schedule quickly, or does it need to ramp?

Ramp it. Extension guidance is to change photoperiod by no more than an hour a week in either direction — a sudden jump can stress the flock. If you're starting supplemental light for the first time in fall, add it gradually rather than jumping straight to the full target.

Does supplemental light shorten a hen's laying life?

It's debated among keepers rather than settled by extension research either way. The mainstream view is that a hen lays a roughly fixed number of eggs over her lifetime regardless of pace, so pushing winter production may not change the lifetime total — it just spreads it out differently. If you'd rather let hens rest through winter, that's a reasonable choice; this calculator just tells you what it takes to keep them laying if you decide to.