Wattage is the amount of power used in an electrical circuit. Wattage is represented with the letter “W” for watts or “P” for power as can be seen in the image of the Ohm’s Law Calculator. When performing load calculations in NEC^® Article 220, wattage is also represented as “volt-amperes” or VA.

Voltage is the electromotive force which pushes electrons through a conductor. Without voltage, current cannot move. It’s no different than water remaining in a garden hose after the faucet is turned off. It cannot go anywhere until the faucet is turned back on and pressure is applied. In the Ohms Law calculator, Voltage is represented by the letter “E”.

A Coulomb is a measurement of the quantity of electrons. Each Coulomb contains 6,250,000,000,000,000,000 electrons.

An Ampere is the measurement of the amount of electricity that flows through a circuit. One amp equals one coulomb per second. Amperes are often represented with “amps” or the letter “A”. In the Ohms Law calculator, the letter “I” stands for the intensity of the current and also represents amperes.

To find missing values using the Ohms Law calculator, simply cover the letter to be determined and either multiply or divide the other two values represented by the remaining letters.

For example:

• To find voltage when only the watts and amperes are known, divide the watts (P) by the current (I).
• To find the current when only the wattage and voltage are known, divide the power by the voltage.
• To find wattage or power when only the amperes and voltage are known, cover the letter P and multiply I x E.