Originally Posted by scambo1

Every aircraft (theoretically) has its weight and balance that exact. However, there is often a tolerance (of allowable slop) on the AWABS (weight and balance) allowing the pilots to add more performance, people or cargo.

The people are either summer or winter weight (slop), cargo is exact weight and station, fuel is exact density within guage error, etc.

So yes and no. It is however all done within specified guidlines.