The humidity level in your incubator can have a big effect on the success of your hatch.
Start by following the instructions that came with your incubator on what humidity level to target, but keep records and improvise from there. The more you incubate and learn from your results, the better your hatch rates will be.
Humidity levels for incubation
I use a tabletop styrofoam incubator for hatching chicken eggs. The guidelines that came with it recommend that you start with 45-55% relative humidity. Keep it in that range for 18 days, then boost the humidity to 55-65% for the next few days until the eggs hatch.
After experimenting with it, I found that I get the best results with a relative humidity near 45% for the first 18 days of incubation. When I’ve tried incubating at closer to 55% relative humidity, far fewer eggs have hatched.
Day 19 is when you remove the egg turner and set the eggs directly on the mesh floor of the incubator. I’ve gotten good results when I increase the humidity to around 55-65% for those last few days of incubation.
In short, I recommend:
- 45% relative humidity for days 1-18
- 55-65% relative humidity for days 19 until the eggs hatch
That’s based on the setup that I am using, my climate, chickens, etc. I don’t know if you will get the same results.
Keep incubation records
Keep records while you’re incubating the eggs.
Several times a day, write down the date, time, humidity and temperature.
Try to keep the temperature and humidity in the incubator as close to constant as you can.
Keep records of how many eggs hatched. How many were fertile? How many weren’t?
For eggs that didn’t hatch, try to figure out why.
Were they infertile? Was there a nutritional deficiency? Was there something you could change with how you are incubating them that might make a difference?
Then make a change and incubate again. Keep records again.
Compare your notes and results, and over time, you’ll learn what works best for you.