Calculator: Basic Ohms Law


An online calculator to calculate your Heater Wattage and Current


It usual happens at time, when a field Technician or an Electrician or an Engineer need to know how much their heater consume Power or how much Ampere their electric heaters draws from the mains. The need can be for installing a new heating system or maintaining the old ones. Whatever it might be the reason, our Ohms law calculator comes handy, whether it is required to calculate heaters Watts, Its Resistance or Its Ampere.

Basics of Ohms Law and Joule Heating

Electric Heater works on the principal of Joule Heating and the relation between Voltage current and Resistance is given by Ohms Law.

Joule Heating

It states that a conductor produces heat, when an electrical current flow through that conductor. Also, because, the relation between Heat generated, and current obeys the Ohms Law, Joule heating is also known as Ohmic heating.

So, How to use this calculator? Let Consider this with some examples

Example 1: Mr X bought a new Industrial Immersion heater for his process, which is rated as 1.5Kw by the manufacturer. Mr X now has no clue of which sized wire to use to power his heater.

Solution: To solve His problem, Mr x uses the above calculator to calculate the amount of current his heater will draw from mains. Now, Mr X knows the Voltage as 230V being available in his area, and he knows that the manufacturer has rated the heater Power as 1.5kw or 1500W. Now He Input this two values into the calculator, and click on “Calculate” button. The Result obtained with these values is Resistance as 35.266Ω and Current as 6.52 amperes. Now Mr X knows that the current will be 6.52 ampere he can now ask his wire men to select a suitable wire that is suitable for this much of ampere.

Example 2: Let consider the same Person, Mr X. Mr X’s Heater, after serving for many years, now fails. He now goes to buy the same type of heater from a local electrical shop. Mr X now identified, that no Power rating is there on the heater. He ask the local shop for the power rating and got a reply that the heater is 1.5kw. He doubt, whether is is really 1.5kw or not.

Solution: Fortunately, Mr X is smart, and have had a multimeter with him. He measures the resistance value between the terminal and note it down. The measured value was 42Ω. He now again uses the above mentioned calculator and input the values. The Values he knows is Resistance is 42Ω and Volt is 230V (Same as in previous example). The values he obtains after clicking the calculate button is Current (I) as 5.47 Amps and Power as 1259.52 watts. He now don’t bought the heater because he now knows that the heater is not of 1500W but is much less 1259.52 watt. Mr X Requirement is of 1500W and thus he leaves from their and order the same heater from the same manufacturer.

Disclaimer: Though this calculator is useful, it is by no means a substitute of a professional Electrician. All the work should be done and handle by a trained electrician and shouldn’t be used by yourself.