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Figuring Volts Watts and Electrical Amperage

How to Calculate Electrical Loads and Circuits using Ohms Law: The Most Common Electrical Calculation using Ohms Law

Understanding and Calculating Electrical Circuit Loads

Electrical Question: I am trying to calculate an electric circuit for my kiln.

Background: David from Brisbane, Australia.
Additional Comments: Seems very helpful and a simple nice clean look.

Dave’s Reply:
Thanks for your electrical question David.

How to Calculate Electrical Loads and Circuits using Ohms Law

The Most Common Electrical Calculation of Ohms Law

To find out the Amperage when the voltage and watts or resistance is known simply make this electrical calculation:
Watts / Volts = Amps
3500 watts / 240 volts = 14.6 amps

More about OHMS Law and Electrical Wiring

Ohms Law Formula
Using the Ohm’s Law is a way to determine information needed to understand how to design electrical circuits.

This formula works with three main variables and depending on what is known can produce a missing factor which is needed to determine the circuit size.

The Ohm’s Law is also used when designing appliances and building electrical equipment and devices.

Electrical wire

Electrical Wire for the Home
Complete listing of electrical wire types and parts used for home projects with electrical code information serves as selection guidelines.

See Also:
Cord and Plug Safety for Electric Kilns

I was given an old, electric jewelry kiln. It draws 14 amps. No identification available. It fires up to about 1650 degrees F., but the plug would get too hot to touch. We replaced the old 2-plug Continue reading

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Frequently Asked Questions and Comments

Questions about Figuring Volts Watts and Electrical Amperage

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  1. Julia k says:

    I want to run outdoor patio lights from one outdoor outlet. How far can I run patio lights 3000 watts, 100 feet strings? I’d like to go 300 feet, can I do that on one outlet?

    • Dave Rongey says:

      Hi Julia,

      The distance an electrical cable may be run to supply power to a device will depend on the following:
      What is the voltage of the devices being powered, in this case, the lights themselves.
      What is the wire size of the circuit supplying the power.
      What is the cable type and that will be installed, and what are the limitations of that cable, such as temperature, amperage, and installation environment.
      What will be the method used to install the cable, such as direct burial or in conduit.

      One rule of thumb is when the length of the cable will be more than 200 feet the size of the cable is increased, however this does not apply to everything, and again, all of the above factors need to be considered as well.

      As you can see, the Device Load, and the Cable Type are Big Factors for any circuit when calculating wire size. This also applies to low voltage lighting as well.

      I hope this helps.


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