Posted by: Harold Ennulat | February 14, 2011

Basic Electrical Formulas

Basic Electrical/Electronic Formulas

Here is a handy Electrical Formula Wheel I found recently on the Web.

These are the basic electrical/electronic formulas I use on a fairly regular basis when doing electrical automation designs. 

These formulas are all derived from 2 simple formulas and these are:

V = I x R 

P = V x I


  • V = Voltage (in Volts)
  • I = Current (in Amps)
  • R = Resistance (in Ohms)
  • P = Power (In Watts)

All of the formulas in the Formula wheel can be derived from the above 2 basic formulas using a little algebra.  In fact this is what I typically do. I derive whatever formula I need starting with the 2 basic formulas and derive the needed formula.  Probably most electrical engineers do this as well I would dare say.  Still it is nice to see these formulas layed out in this wheel format.  It shows the power of learning just 2 simple formulas.


For those new to the basic calculations used in electrical design or those that want a quick reference they can use throughout their careers I recommend “Ugly’s Electrical References“.  In addition to providing these simple formulas it also is a great reference for doing 3 phase power calculations and converted between single phase and 3 phase power equivalents.  I find myself turning to this reference over and over.  For example, It seems I regularly turn to this reference when doing power calculations since as a controls engineer I need to refresh myself when doing 3 phase power calculations.  Ugly’s also contains motor and conduit sizing tables from the NEC (National Electric Code) book as well as other valuable information, all in a back pocket-sized reference.

Updated: March 5, 2011  |  Created: Feb 14, 2011

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