In trying to learn the relationship between the length of a steel column and its buckling stress, Eulers formula of F=PI^2EI/(KL)^2 seems to be it, and points to the fact that the force is inversely proportional to the square of the length.
So why should it be that when I try different lengths in the online calculator, halving or doubling the length seems to make very little difference to the allowable force at all.
The lengths tried in the calculator were all at least critical slenderness ratio or longer. | 
