# Perry Robertson formula

The Perry-Robertson formula is a mathematical formula which is able to produce a good approximation of buckling loads in long slender beams, and is the basis for the buckling formulation adopted in EN 1993. The formula in question can be expressed in the following form:

where:

Robertson then proposed that ${\displaystyle \theta =0.003\lambda }$, where ${\displaystyle \lambda }$ represents the beam's slenderness.