Well... Are you talking about a home network?
There are tests made on Tom's Hardware. For a wireless network, you can use your computers for a distance of approximatively 30-50 meters from AP. If you are lucky.
For a wired network, you can use your computers for a distance of 100 meters from hub/switch/router (I am talking about Ethernet, with cat 5 cable).
If we are talking about an industrial LAN... Well, we are talking about much extended networks.
Why do you ask?