Electrical Calcuations

The relationship between voltage, current and resistance is defined by Ohm's law, and power by Joule's law.

Ohm's Law:- Ohm's law E=I*R
Joule's Law:- Joule's law P=E*I
where:-
E = Voltage (in volts)
R = Resistance (in ohms)
 
I = Current (in amps)
P = Power (in watts)

These formulae can also be conveniently placed in a formula wheel.
Just use the relevant ones for your calculation.

Given any 2 of the above values, it is possible to calculate the others:

Electrical Calculator
Enter two values to find the other values.
Voltage: Volts
Current: Amps
Resistance: Ohms
Power: Watts
   

Series Resistor Calculator

Enter resistor values to calculate the total resistance.
R1: ohms
R2: ohms
R3: ohms
Rtot: ?? ohms
   
Parallel Resistor Calculator

Enter any two of the following values to calculate the third.
R1: ohms
R2: ohms
Rtot: ohms