How do you tell a male chicken egg from an female chicken egg?

Answer:
Until they hatch, you can't.

Edit added: Very true; so don't buy any of the so called 'egg-sexing' swing magnets and other devices sometimes offered for sale on Ebay!

They don't work! If they did work, don't you think hatcheries producing layer hybrid chicks would use them, thereby saving themselves millions of £/$/whatever?
First answer by ID2092264655. Last edit by DaveScriv. Contributor trust: 3 [recommend contributor recommended]. Question popularity: 1 [recommend question].