You might assume (like I did) that if you put ten eggs in your incubator, you'll end up with ten chicks, but there's a lot that can go wrong before your chicks hatch. Assuming you do everything right, what kind of hatch rate is a backyard hobbyist looking at?
Browsing through chicken books from the early 1900s, I came across hatch rates from a time when incubators were still in their infancy. During this period, many of the small and mid-size chicken farms were still raised new chicks each year using broody hens, which gave them hatch rates of 45% to 65%. Larger farms (and those raising the new, unbroody varieties) were moving over to artificial incubation and netted 30% to 79% living chicks, with the average hovering around 50%.
For information on modern incubation technology, I turned to random accounts on the internet. (I know, not very scientific, but if you look at enough of them....) When hatching homegrown eggs that haven't sat around very long, it sounds like you might manage to get 75% to 80% (sometimes hatching all of your eggs but sometimes having runs where you hatch far fewer.) For shipped eggs, 50% hatch seems to be about average.
I've had a steep learning curve during my first two hatches. My first hatch had major problems with temperature and humidity control and I also used less viable eggs from old hens, so I ended up with only 17% living chicks. For my second hatch, I improved on the environmental conditions but still used old eggs in half of the incubator, comparing them to mail order eggs from prime breeding stock. My hatch rates there were 25% and 58%, respectively. I had hoped to improve my hatch rate yet again for my third incubator run by using only squeaky clean eggs, but it sounds like since my eggs will be all mail ordered, I should probably expect around a 50% hatch. I'll let you know how it goes in the middle of June
