The assessment of buckling resistance of beams and beam-columns requires the computation of the elastic critical moment, which strongly depends on both bending moment diagram and end support restrictions. These two effects are usually considered as uncoupled: bending moment distribution is taken into account by an equivalent uniform moment factor (EUMF), and end support restrictions are introduced through buckling length. Some modern steelworks design codes provide closed form expressions to compute the EUFM for any bending moment distribution, but changes in the moment factor due to end support restrictions are not considered. The paper first presents a general review of moment factor values offered by modern steelworks standards. Then these values are compared with those provided by recent and traditional technical papers. Finally a new general closed form expression to compute the EUMF for any moment distribution and support conditions is presented.