In many fantasy worlds, giants are as intelligent as human beings and others races that they either avoid stepping on or step on regularly. However, due to the square cube law, giants have a limited size where they can exist; but due to again the square cube law, the larger you are, the harder it is to keep a powerful brain up and running. Thus, my question in:
How big can a giant get before getting to big to support a complex brain?
The giants them selves will be confined to the laws of physics, and thus no magic is allowed.
Also, these giants will be confined to the land and be adapted to such an environment (Large feet, stocky build, etc.) So no water buoyancy to help them.
Edit. Due to the need for clarification as to why giants would loose human intelligence as thy get bigger, I will put a brief explanation on the issue of large, bipedal intelligence. The issue, per usual, is the Square Cube Law. I.e, the bigger something gets, its surface area goes up by square but the volume goes up by cube. This leads, to large bipedal any way, a need for increased muscle mass and bone structure. However, that new mass needs support to. This results in a viscous cycle where the organism would eventually get crushed under its own weight. Thus, weight savings need to be made, and for giants, the most likely weight saving measure that s first to go is intelligence. Here is a link for a video that explains it with more detail here
