Forced air (fan equipped) 99.5. Still air, 100.5 at the top of the eggs. https://www.backyardchickens.com/a/hatching-eggs-101
Still air incubator, 102 degrees on top of the eggs, Forced fan incubator, 99.5-100 degrees measured anywhere in the incubator. Always use more than one thermometer (especially in a still air) and make sure your thermometers are accurate.
