What Is an Egg Incubator? Simple Guide + 21-Day Timeline

An egg incubator is a small machine that helps eggs hatch without a broody hen. It keeps the right temperature, humidity, airflow, and it turns the eggs on a schedule so the embryos can grow.

Quick takeaways

• For chicken eggs in a forced‑air incubator, a common target is 99.5°F (37.5°C).

• Humidity is often 40–50% for Days 1–17, then 65–75% for Days 18–21 (called lockdown).

• Turn eggs several times a day until Day 18, then stop.

• Keep fresh air moving, especially late in the hatch.

How Does an Incubator Work?

All incubators manage four simple things:

1. Heat
   A thermostat runs a heater to hold a steady temperature. Forced‑air models use a fan for even heat. Still‑air models do not. In still‑air units, the top of the eggs is warmer, so you often aim 101–102°F (38.3–38.9°C) measured at the egg tops.

2. Humidity
   Water trays, channels, or a small sponge add moisture. The goal is steady water loss inside the egg so the air cell grows to the right size by hatch.

3. Ventilation
   Vents or a fan bring in oxygen and remove carbon dioxide. Do not close vents during the last days.

4. Turning
   Turning keeps the embryo from sticking to the shell membranes and helps it grow in the right position. Stop turning on Day 18 for chickens.

Common Types

• Forced‑air vs. still‑air — Fan vs. no fan. Forced‑air is easier for beginners.

• Desktop vs. cabinet — Small countertop units (6–60 eggs) vs. large boxes that hold hundreds of eggs.

• Manual vs. automatic turning — Hand‑turn 3–5×/day, or use an automatic turner.

• Analog vs. digital control — Digital models add alarms and built‑in sensors.

Tip: Calibrate your thermometer and hygrometer. Built‑in displays can be off by 0.5–2.0°F.

Quick Start (Beginner Setup)

1. Place & preheat the incubator in a draft‑free room, away from windows. Level the unit and warm it up to your target temp.

2. Check your tools. Use a reliable thermometer and hygrometer. Do a quick check before setting eggs.

3. Add water to the right channels to reach a baseline 40–50% RH.

4. Load eggs pointy end down. Start the automatic turner, or plan to turn 3–5 times/day by hand.

5. Daily check. Peek fast, close fast. Make small, slow changes.

6. Day 18 = Lockdown. Remove the turner, lay eggs on the hatching tray, raise humidity to ~65–75%, open vents, and stop opening the lid unless needed.

21‑Day Hatching Timeline (Chicken Eggs)

These are typical targets for a forced‑air incubator. For still‑air, measure at the egg tops and keep it ~101–102°F until lockdown. Always follow your model’s manual.

Adjust by air‑cell: Too small → lower RH (more evaporation). Too large → raise RH (less evaporation).

Fast Troubleshooting

• Late quitters: often temp or humidity swings, weak ventilation, or opening during hatch.

• Sticky chicks / shrink‑wrap: humidity too low in lockdown.

• Edgy thermals: aim for small, slow changes. Big swings hurt hatch rates.

FAQs

1) What temperature should I use?
For forced‑air units, 99.5°F (37.5°C) is common. For still‑air, measure at the egg tops and use 101–102°F (38.3–38.9°C).

2) What humidity should I use?
Many hatchers run ~40–50% for Days 1–17 and ~65–75% for Days 18–21. Validate by air‑cell growth or ~11–14% egg weight loss by Day 18.

3) Do I really have to turn eggs?
Yes—until Day 18. Manual: 3–5 times/day. Automatic: let it run.

4) What is “lockdown”?
From Day 18: stop turning, raise humidity, open vents, and avoid opening the lid. Stable air helps safe pipping and hatching.

5) Forced‑air vs. still‑air—what’s easier?
Forced‑air is more forgiving. Still‑air works too, but you must watch placement and temp at the egg tops.

6) Can I wash eggs before I set them?
Use clean, unwashed eggs when possible. Washing removes the protective bloom and can raise contamination risk.

7) Do ducks, quail, or turkeys use the same settings?
No. Days to hatch and humidity targets change by species. Some waterfowl also benefit from brief cooling or misting late in incubation.