What's the correct humidity for hatching chickens?

Incubator humidity is one of the most discussed subjects in incubation and chicken keeping. It's open to a great deal of debate, resulting in many anxious nights for first timers and experienced breeders alike.

The first rule of incubation humidity: Don’t panic!

Unlike temperature - which needs to be kept constant - humidity can vary greatly without having any adverse effect on your hatch. Guidelines suggest an average humidity level of 50-55%. But in reality, keeping within such a tight range is almost impossible, even for incubators with full humidity control (such as the Rcom King Suro Max 20, below). Your actual humidity levels are likely to vary, up and down - between 40% up to around 65%, before heading back down again. This is perfectly normal and nothing to be concerned about.

Aim for 52% Relative Humidity. But remember:  this is only a target, not a steadfast rule. If your incubator is set to a humidity level of 55%, while the actual humidity levels will fluctuate, it will average at the set level.