If you mean you physically, as in how many pounds can you carry before it is too much, then it depends on the person. Some people are small and can't carry too much while others are professional body...
Typically under 50 pounds for checked, 30 pounds for carryon. Anything above this will result in more fees. Usually nothing over 100 pounds is allowed at all.
All aircraft have a certain weight limit that must not be exceeded for safety reasons. By figuring the number of people and luggage items the plane will carry, the airline can decide what the maximum...