How To Calculate Cable Size In Sq Mm Formula -The most reliable formula for cable sizing (especially for longer runs) uses voltage drop as the limiting factor. For a single-phase AC or DC circuit: For a three-phase circuit: [ A = \frac2 \times \rho \times I \times LV_d ] how to calculate cable size in sq mm formula [ A = \frac\sqrt3 \times \rho \times I \times LV_d ] The most reliable formula for cable sizing (especially |