Electrical Installation Design How to carry out cable calculations to correctly size your electrical conductors Design Current Protective devices Current carrying capacity Volt drop Sizing of the MCB/Fuse and more... At 21.29 you might spot I used the In instead of Ib in the volt drop calculation. So 16A instead of 13.04 A Volt drop is actually 13.23v not 16.24v Still unsuitable cable though 22.16 Maths error Ib x L