Not sure what you need to calculate. More words to explain your question would be great.

I can offer Ohm's Law:

Electrical load calculation for what?

How calculate the voltage drope in cable

Vd=2 times length of wire times amps times ohms per foot of wire.

If 3 phase , multiply by .866

Is that what you wanted to know? Your cryptic question didn't allow much speculation. A more precise and direct question as to what you are trying to cypher would make it easier for many of us to answer.