The shear flow formula provides a means for computing the amount of force that must be transmitted between connected parts in a beam:

where q = shear flow (force per unit length of beam span), V = shear force, and I = moment of inertia.

The section property Q found in the shear flow formula relates to the net horizontal resultant force produced by the bending stress distribution acting on a specific region of the cross-sectional area. Q is defined as the first moment of this area about the centroidal axis for the complete cross section.