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Incubator Temperature and Humidity for Chicken Eggs: Little Giant's Directions

What temperature and humidity to run an incubator at for chicken eggs, when to turn, candle and lock down — from Miller's Little Giant instructions.

Short answer: Miller Manufacturing's instructions for its Little Giant incubators say "The Incubator comes preset to 99.5°F (37.5°C for Model 12500)" and "The ideal average temperature to incubate the majority of eggs is 99.5-100°F." For humidity, the same instructions give a typical range of about 45–55% during incubation and about 60–70% for the last 3 days before hatching. Those are the maker's figures for its own incubators; the instructions also suggest a local college or university agricultural department for more on humidity levels.

This guide sets out what Miller's Little Giant instructions say, step by step, and the incubating and brooding equipment we list. It is not a substitute for the instructions that come with your incubator.

What temperature should an incubator be for chicken eggs?

  • Miller: "The Incubator comes preset to 99.5°F (37.5°C for Model 12500)"
  • "The ideal average temperature to incubate the majority of eggs is 99.5-100°F."
  • "This average temp can range from 98 and 102 degrees F." (98–102°F is about 36.7–38.9°C — our conversion.)
  • "If the temperature is about 1 degree too high from optimal, eggs may hatch around 1 day early."
  • "If the temperature is about 1 degree too low from optimal, eggs may hatch around 1 day later."

Where the incubator sits matters too. Miller's troubleshooting section asks for a room with a consistent temperature of 65–72°F (about 18–22°C), away from drafts, and says: "Do Not use an incubator in a drafty environment."

Before any eggs go in: "Prior to putting eggs in the Incubator, run the incubator for at least 4-8 hours to ensure the incubator is holding your desired setting temperature and humidity." Miller also notes: "Some users choose to use a secondary thermometer/hygrometer to verify the incubator temperature and humidity." The Little Giant Incubator Thermometer Kit is one we list.

How many days to hatch, and at what temperature?

Miller's chart of estimated days to hatching and hatching temperature (°F):

  • Chicken: 21 days, 99.5°F
  • Bobwhite quail: 23 days, 99.5°F
  • Coturnix quail: 17–18 days, 99.9°F
  • Pheasant: 23–28 days, 99.5°F
  • Chukar: 23–24 days, 99.5°F
  • Turkey: 28 days, 99°F

The chart's days are estimates. Miller also says: "For example, it is not recommended that you attempt to hatch chicken and quail eggs at the same time in the same incubator."

What humidity should an incubator be?

Miller's instructions put humidity typically at about 45–55% during incubation and about 60–70% during the last 3 days before hatching, when the chick turns inside the shell to break out. On the Little Giant, humidity is set with the water channels in the base:

  • "Fill 1-2 channels with water and run the incubator for a couple hours to allow the temp and humidity to stabilize."
  • "The total surface area of water will determine your humidity and not the depth of the water in the channel."
  • "Drier climates may need more water channels filled than Humid climates to reach the same humidity inside the incubator."
  • "If the windows are completely fogged over or completely covered in condensation, your humidity levels may be too high."
  • "Setting humidity can be a trial-and-error process."

Before you set the eggs

Miller says fertilized eggs should be stored no more than 10–14 days at 50–60°F (10–15.5°C) before incubating, and prints, in capitals: "DO NOT REFRIGERATE."

  • "Prior to placing eggs in the incubator, bring eggs to room temperature."
  • "Do not put cold eggs directly into a warm incubator as the temperature shock could lead to decreased hatch rates."
  • "If using the Automatic Egg Turner, place eggs into each cavity with the small end down."
  • "Do not open the incubator for the first day after the eggs are set."

How often do you turn eggs in an incubator?

  • "If not using the Automatic Egg Turner, turn eggs at least 2-3 times per day at the same time every day."
  • "Stop turning the eggs 3 days prior to hatch."

An egg turner does the turning for you; we list the Little Giant CSA-listed Egg Turner. Miller's instructions note: "Turkey eggs will not fit in the Automatic Egg Turner."

Candling

Candling is optional in Miller's instructions — a way to check that embryos are developing and to find eggs that are not fertile. As we read Miller's fertility-testing chart, white or clear-shelled eggs are first checked on the 3rd or 4th day of incubation and dark-shelled eggs on the 7th or 8th day, with a second check on the 14th day for both. Miller's tip: "Test in a dark room for best results." We list the Little Giant Egg Candler.

Lockdown and hatching

  • "When you have 3 days remaining until hatch (called lockdown), stop manually turning the eggs or if using the Egg Turner, remove the Egg Turner and gently place the eggs on the floor screen."
  • At lockdown, Miller's instructions raise humidity by filling more water channels.
  • "Do not open the Incubator except to remove chicks."
  • "Avoid opening the lid more than necessary as every time the lid is opened, the warm air and humidity inside will escape."
  • "Some chicks may hatch late, so continue to run the incubator for a few extra days beyond the normal hatch period."
  • "Do not use the incubator as a brooder."

Once chicks are out, they move to a brooder. Our guide Chicken Coop Heaters for an Alberta Winter: Heated Perches, Pads and Brooders covers brooder heat, Chick Starter, Grower or Layer Feed: When to Switch Chickens covers the starter ration by Masterfeeds' directions, and Chicken Waterers and Feeders: Types, Height and Cleaning (Alberta Small-Flock Guide) covers drinkers and feeders.

Incubating and brooding equipment we list

Follow the instructions that come with your incubator, turner and brooder; where they differ from this summary, they take priority.

Sources: Miller Manufacturing, Little Giant incubator instructions (complete instructions PDF, including the estimated-days chart and the fertility-testing chart) and the Digital Egg Incubators product page, miller-mfg.com, viewed October 2026. Temperatures in °C other than Miller's own are our conversions.