Does egg shape indicate chick sex?

Lately I've been seeing some information going around that claims that you can choose which gender chick you hatch by carefully selecting the shape of the eggs you incubate. According to this information, round eggs hatch pullets and more pointed or oval eggs hatch cockerels. It's an interesting concept but completely untrue.
Round eggs hatch female chicks

First of all this didn't make sense at all to me because over the years I've always incubated oval shaped eggs. In the post How to store and handle hatching eggs I talked about how odd shaped eggs should not be hatched and that they don't get as good a hatch rate as your regular, well...egg shaped eggs. Except for a few experiments with pullet eggs, I always set oval shaped eggs.

If the round egg myth was correct, I would have hatched an excess of cockerels on every hatch. That's not what happened.

Do hens hatch from round eggs?

Over the years I've hatched roughly 50% males and 50% females from those oval eggs. So obviously oval eggs can't have a greater chance of being male if I'm getting about 50/50 from them. Of course with my different breeding group sometimes I had a group that threw a lot of females and sometimes I'd have breeding groups that threw a lot of males but over the years when I look back at all the information it comes out to roughly 50/50.

My experimental hatch of round eggs

I decided to do an experiment. One of my hens went broody so I gave her 10 of the roundest eggs I could find. I literally laid out all the eggs I had on their sides and picked out the roundest of the bunch. I starred the ones I chose in the picture.

Rounds eggs hatch more hens

One of those eggs quit in the first few days, but she kept sitting on the other nine. She hatched seven of them. These chicks are almost 3 weeks old but it's becoming very obvious how many males and how many females are in the group.

These results totally destroy the round egg = pullet myth. As you can see at least 3 out of 7 are male. That's not really good odds of you ask me! In fact, it's as close as you can get to 50/50 with an odd number. Of course if you want the round egg thing to be true, we can always claim those 3 eggs that didn't hatch were all female. It can't be proven of course, but I don't really believe that anyway. 

Round eggs do not hatch pullets only

I know the picture is a little blurry for a few of the other chicks, but it's really hard to catch a picture of 7 chicks all standing perfectly still! I did manage to capture the combs on the boys though. Of course I've got 20 more pictures of blurry chicks if you want to see them. lol

Incubate all round eggs

Don't take my word for it though, you should do your own experiment. Set an entire hatch of round eggs, or set an entire hatch of regular shaped eggs. See how many pullets and how many cockerels hatch. I'd love to hear your results! 

I've been chatting with lots of chicken keepers about this and everyone seems to be getting different results. The fact that it doesn't 'work' for everyone though, pretty much busts the myth right there.

Chances are, if you think back on the hatches you've had over the years you will realize that the majority of the eggs you've set were oval. We tend to avoid the odd shaped eggs when choosing from our own, and reputable breeders ship out only the most perfectly shaped eggs for hatching.

How to hatch all hens with temperature changes

While thinking about past hatches (or checking data if you write everything down like I do) you also have to consider any problems you had with the heat controls in your incubator. Many people believe that lower temperatures in the incubator (I'm talking like a half a degree) produce more females and a slightly higher temperature or even a temperature spike, produces more males.

It's not that the temperature actually influences what will come out of each egg, it's that the eggs that quit developing after the temp  spikes are believed to be female. The eggs that quit at a slightly lower than ideal temperature are believed to have been males. 

Of course there is no hard proof of this. Nobody has actually DNA tested the eggs that quit developing after a temperature change. As of now it's all just theory and experimentation.

Have you tried hatching all round eggs to get all pullets? Let me know in the comments what your male to female ratio was! I'd love to hear all about it!

Want to know more about incubation and hatching chicks? Click here for The only hatching guide you'll ever need!


Want information on raising chickens sent right to your email weekly? Click right here to join my list and get new posts sent directly to you the day they're published ... plus, you'll also get the free download '25 Ways to save money raising chickens'.


  1. Love your blog and that you actually take issues like this and get some evidence rather than spreading myths. Keep the information coming, you are a great inspiration!

  2. I tested it as well, Put 10 eggs under the hen and got 7 pullets and 3 roosters

  3. Hello! I studied this issue long enough and carefully. I can say that the sex of the future chick is determined during the formation of the egg. Therefore, the shape of the egg, incubation temperature, etc. do not affect the sex of the future chicken. There are several interesting observations: in the spring there are more cockerels, and in the fall there are more hens; If you cool the eggs before incubation to +4°C, male embryos die, female embryos remain viable. Best Regards, and I apologize for my English.