Hatching

Incubator Chart: Temperature, Humidity, Turning and Candling Days for Chicken Eggs

Field guide · Updated October 26, 2026 · about 8 min read

An incubator does the hen's work by the numbers: steady heat, the right humidity, regular turning, then three quiet days while the chicks hatch. This chart lines up what university extension services recommend for chicken eggs, phase by phase, and shows where the sources disagree. For hatching under a hen instead, see broody hens and the 21-day timeline.

Settings at a glance

Setting	Forced-air (fan)	Still-air (no fan)
Temperature	99.5°F (Missouri, Maryland); 99–100°F (Oklahoma State, Illinois); 100°F (Mississippi State)	100–102°F, acceptable range 97–102°F (Missouri); 102°F at the top of the eggs, 2–3°F above forced-air (Mississippi State); 101°F week 1, 102°F week 2, 103°F to hatch (Oklahoma State)
Where to measure	At egg level. Still-air units vary considerably from top to bottom (Oklahoma State), so measure at the top of the eggs (Mississippi State) or 1 inch above the wire mesh (Missouri), with the bulb not touching eggs or the incubator
Humidity, days 1–17/18	55–60% (Maryland); 58–60% (Mississippi State); 60% (Illinois, Oklahoma State); 60–65% (Missouri)
Humidity, last 3 days	65% or more (Mississippi State); 70% (Missouri, Illinois; Maryland and Oklahoma State from the first pip)
Turning	At least 3 times a day, an odd number (Missouri, Illinois); at least 4 (Oklahoma State); 4–6 (Mississippi State); 5–6 (Maryland)
Stop turning	After day 17 (Missouri, Illinois) or day 18 (Maryland, Mississippi State, Utah State)
Incubation period	21 days (all sources)

Follow your incubator's manual where it differs; Utah State adjusts humidity "per the incubator's instructions." Mississippi State runs still-air machines 2–3°F warmer than forced-air ones.

Temperature: small errors matter

Half a degree. Missouri Extension says each 0.5°F change in average temperature shifts hatch time by about 5.4 hours. Utah State: "Even a half of a degree makes a huge difference."
One degree. Variations of more than one degree from the optimum reduce hatchability (Oklahoma State). Mississippi State tolerates swings under ½°F but no more than 1°F in total.
Too hot. Running at 105°F for 30 minutes can seriously affect or kill embryos (Missouri); 103°F for 4 hours causes high mortality (Illinois). High temperatures bring an early hatch (Maryland, Utah State).
Too cool. Low temperatures slow development and bring late hatches (Illinois, Maryland, Utah State).
Thermometers. Use two if possible and calibrate them (Illinois); check against a clinical or lab thermometer (Mississippi State). Maryland puts a second thermometer at egg level to confirm the unit works.
The first two days. Expect a temperature drop when cool eggs go in; Illinois says not to turn up the heat during the first 48 hours.

Humidity and the air cell

Most home incubators hold humidity with a water reservoir, read with a wet-bulb thermometer (Utah State). Mississippi State's conversions at a 100°F dry bulb:

Relative humidity	55%	60%	65%	70%
Wet-bulb reading	85.3°F	87.3°F	89.0°F	90.7°F

As water evaporates through the shell, the egg should lose weight: 11–14% from day 1 to day 18 (Missouri) or about 12% (Mississippi State). The air cell shows whether that is on track. It should grow throughout incubation (Utah State); a large air cell means humidity is too low and a small one means it is too high (Missouri). Mississippi State checks air cell size at days 7, 14 and 18.

Turning

Set eggs large end up, or on their side with the large end slightly raised. Never small end up: Oklahoma State says that gives "an extremely poor hatch."
Mark the eggs. Hand-turners mark an X on one side and an O on the other in pencil (Illinois, Mississippi State).
Turn gently, through 90 degrees (Oklahoma State), and avoid full-circle rotations (Missouri). Missouri recommends an odd number of turns (5, 7 or 9): first thing in the morning, last thing in the evening and once or twice in between. Utah State recommends an automatic turner.
Why it matters: eggs that are not turned enough let the embryo stick to the shell (Maryland, Oklahoma State).
Stop at day 17 or 18. Missouri notes research suggests turning is unnecessary after about day 14, though many systems continue to day 17–19.

Day-by-day incubator chart

Day	What to do
Before day 0	Test the incubator 2 weeks ahead and start it 2 days before setting (Illinois); Maryland says at least 24 hours. Room at 70–75°F, away from drafts and windows (Illinois).
0	Let stored eggs warm to room temperature first, 30 minutes to 2 hours (Illinois); moving eggs straight from 55°F to 100°F causes condensation (Mississippi State). Set them and note the date.
1–17	Hold temperature and humidity; turn daily; check the reservoir water daily (Maryland).
6–10	Illinois candles once in this window, keeping eggs out no more than 5 minutes.
7	Utah State's first candling: a healthy embryo shows veins reaching the shell; remove clear (infertile) eggs and eggs with a ring and no veins.
10	Maryland candles after day 10: infertile eggs look bright, growing embryos dark. Remove dead and infertile eggs; they can burst.
12–13	Illinois: "exploders" usually occur around now.
14	A chick can usually be seen; avoid candling after this (Utah State). Missouri instead candles 3–4 days before hatch.
17–18	Lockdown: stop turning, raise humidity, move eggs to the hatching tray if there is one (Utah State), and open the vents more (Mississippi State).
19–20	The yolk sac moves into the body; on day 20 the chick starts breathing and pips (Oklahoma State). Illinois: all yolk must be absorbed by the end of day 20.
21	Hatch. Keep the lid closed (Utah State, Mississippi State).
22 and after	Remove chicks once dry and fluffy (Illinois); Mississippi State says within 24 hours of hatching. Illinois removes unhatched eggs 60 hours after the first chick hatches; Utah State says chicks not out one or two days after the hatching period likely will not survive.

Turn at least 3–6 times a day, depending on the source, from day 0.
Stop turning after day 17 or 18.
Humidity about 60% (sources give 55–65%) until the last three days.
Raise humidity to 65–70% for hatching.
Day 7: first candling; veins reach the shell (Utah State).
Day 10: infertile eggs bright, growing embryos dark (Maryland).
Day 14: chick usually visible; avoid candling after this (Utah State).
Lockdown: keep the lid closed and open the vents more.
Day 20: chick pips and starts breathing air.
Day 21: hatch.

Chart drawn by HenClass from the Missouri, Maryland, Mississippi State, Oklahoma State, Illinois and Utah State Extension publications cited on this page. Days are spaced to scale; bar heights are not to scale.

Lockdown: the last three days

Keepers often call days 18–21 "lockdown"; the extension sources simply describe the steps.

Keep the lid shut. Once hatching begins, Mississippi State says not to open the incubator until all chicks have hatched; low humidity can damage membranes within 1 to 2 minutes of opening it, trapping chicks that are pipping.
Raising humidity. Utah State raises it by closing vents or adding water, following the incubator's instructions; Illinois adds sponges at the end of day 17. Mississippi State warns against closing vents at hatch, because oxygen need peaks on the last day: "Never decrease ventilation openings at hatching in an attempt to increase humidity." Its advice is to add water evaporation instead.
Do not pull chicks out. Helping a chick from the shell carries risk (Maryland); Utah State says such attempts are usually unsuccessful.

Hatch troubleshooting

Missouri Extension says about two in 10 eggs normally fail to hatch. When far more fail, the pattern points to a cause.

What you find	Likely causes
Clear eggs, no development	Infertile eggs or very early death (Missouri); eggs stored too long or incorrectly (Mississippi State)
Blood ring or tiny embryo	Death in the first three days from incubator malfunction or poor storage (Missouri); wrong incubation temperature (Mississippi State)
Many early dead embryos	Temperature too high, too little turning, poor ventilation (Mississippi State)
Fully formed chicks that did not pip	Low average temperature, low humidity, weak embryos (Missouri)
Pipped but died in the shell	Too little humidity or ventilation at hatch, malpositioned embryos (Mississippi State); too much humidity earlier can leave the chick to drown in leftover fluid (Mississippi State)
Dry chicks with shell stuck to the down	Low humidity after pipping began (Missouri); excessive ventilation (Mississippi State)
Sticky chicks smeared with egg contents	High average humidity, low temperature, poor ventilation (Mississippi State)
Early hatch, bloody navels	Temperature too high or swinging too widely (Missouri, Mississippi State)
Late or uneven hatch	Low temperature, warm and cool spots in the incubator, old eggs (Mississippi State)
Large, mushy chicks with a bad odor	Low temperature and poor ventilation, or navel infection; clean and disinfect between hatches (Mississippi State)

Before you set eggs

Storage temperature. 45–55°F (Missouri); 55°F at 75% humidity (Mississippi State's Care and Incubation guide); 55–60°F, such as a refrigerator's vegetable drawer (Illinois). Missouri says a household refrigerator at 40–45°F is too cold.
Storage time. No more than 7 days (Mississippi State); never more than two weeks, best within three to four days (Missouri). Do not wash hatching eggs (Illinois).
Cleaning. Missouri cleans incubators with 20 drops of bleach per quart of water.
Power outage. Illinois: cover the incubator with a large cardboard box; some embryos survive below 90°F for up to 18 hours.

Once chicks are dry, move them to a brooder already running: the chick care checklist covers temperatures week by week, and heat lamp safety covers the heat source. Hatching terms such as pip and candling are in the glossary. HenClass does not give veterinary advice; for sick chicks, contact a veterinarian or your county extension office.