Egg Fertility Calculator — Candling Schedule
Select your species and the date eggs were set to get a complete candling schedule, including what a fertile egg should look like at each stage and when to go into lockdown.
Quick Answer
Candle eggs at roughly day 7, day 14, and 3 days before hatch (lockdown) for most poultry species. Select your species and set date above for exact candling dates and what to look for.
Egg Fertility & Candling Calculator
Free tool — no signup required
Day 7 Candling: Fertile vs. Clear
At the first candling, a fertile egg shows a network of thin, spider-web-like blood vessels radiating from a small dark spot (the developing embryo), often called the "spider" appearance. A clear, uniformly yellow-orange interior with no visible structure means the egg is infertile or development stopped very early — these should be removed to avoid contaminating the incubator if they rot. A reddish blood ring around the inside of the shell indicates the embryo started developing but died early, and these eggs should also be removed promptly.
Day 14 Candling: Checking Development
By the second candling, the embryo should be noticeably larger, appearing as a dark, irregularly shaped mass that may shift slightly when the egg is moved, and the air cell at the wide end of the egg should be visibly larger than at the first candling. You may also see movement if you hold still and watch for a few seconds — a good sign of an actively developing, healthy embryo.
Lockdown Timing
Lockdown timing depends on species: chicken eggs go into lockdown around day 18 (3 days before the day-21 hatch), duck and turkey eggs around day 25, goose eggs around day 27, and quail eggs around day 15. At lockdown, stop turning the eggs, raise humidity significantly, and minimize opening the incubator to preserve humidity for hatching — every time the incubator is opened during this window, hard-won humidity escapes.
Detecting a Pip & Assisted Hatching
In the final day or two before hatching, you may hear faint peeping or scratching sounds from inside the egg, and candling (done briefly and gently at this late stage) may show the chick positioned with its head under its wing near the air cell, ready to pip. Assisted hatching is controversial and should be a last resort — most chicks that pip successfully complete hatching within 24 hours without help, and intervening too early can cause fatal bleeding if the yolk sac hasn't fully absorbed.
How We Calculate the Candling Schedule
The calculator uses standard candling milestones (approximately day 7, day 14, and 3 days before expected hatch for lockdown) scaled to each species' total incubation length, drawn from published poultry husbandry references.
Frequently Asked Questions
Sources & References
- Merck Veterinary Manual — Poultry incubation and hatching
GestationCalc Editorial Team
Our editorial team includes animal husbandry specialists, veterinary consultants, and agricultural extension educators. Content is reviewed against peer-reviewed research and guidance from USDA, Penn State Extension, and the Merck Veterinary Manual.
Last reviewed: September 5, 2026