In the four tables below, you may enter two of the four factors in Ohm's Law. They are Power (P) or (W), measured in Watts, Voltage (V) or (E), measured in Volts, Current or Amperage (I), measured in Amps (Amperes), and Resistance (R) measured in Ohms. The needed factor will be calculated for you when you click on the Calculate button for that table.

Though not part of the original theory, in later years, we have also attributed the Power factor to Ohm as well. Power is usually abbreviated by (W) and measured in Watts. The formula generally given for Power is:
W = V x I or W = I^{2} x R or W = V^{2} / R. Other basic formulae involving Power are:
I = W / V or I = (W / R)_{2}
V = (W x R)_{2} or V = W / I
R = V^{2} / W or R = W / I^{2}

Resistivity (W-cm) for Common Metals
at Room Temperature

Aluminum

2.828 x 10^{-6}

Copper

1.676 x 10^{-6}

Silver

1.586 x 10^{-6}

Gold

2.214 x 10^{-6}

Tungsten

5.510 x 10^{-6}

For example, a 10 Gauge wire is 2.588mm in diameter.
The resistance per cm of copper wire that thick is
3.186 x 10^{-5}W/cm.
A mile of this wire has a resistance of 5.13 W.