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how to calculate voltage, wattage and resistance

How To Calculate Voltage, Wattage, And Resistance

  |   Electronics   |   No comment

Most people outside the engineering field don’t really understand the difference between voltage, watts, ohms, and amps. While they do encounter all of these terms in their day-to-day life, they don’t understand how they affect the performance of the electronics and electrical equipment. However, if you understand what these concepts are and how they’re connected to one another, you’ll be able to understand your electrical equipment and electronics better. Here’s a brief explanation of these concepts.

What are They?

To understand how to calculate voltage, wattage, and resistance, you need to understand what they are.


Voltage is known as an electromotive force. It defines the potential difference in charge between two sections of an electric field. You can consider it akin to water pressure. The higher the voltage, the greater the flow of electrical current.


Watt is an SI unit and showcases the measure of power. It measures the rate at which energy is dissipated, radiated, or absorbed. That’s one of the reasons why light bulbs and other such electrical fixtures.

Electrical Resistance

As electricity moves, its power reduces and fades a little. Electrical resistance is similar to this concept. When power moves through an electrical device, the current flow slows down. So resistance is a unit that measures just how much the current flow can actually slow down. It’s usually measured in ohms. You can compare this to the flow of water through pipes. The thinner the pipe, the higher the resistance.


The rate of flow of electrical current is measured in amps. Current is directly related to voltage. So, if the voltage is high, the flow of current will be high as well. This is usually featured in your energy bills as it showcases just how much power you draw from the main line.

How to Calculate Them

If you want to calculate these units, you need the values of other units. There are many different formulas out there that would help you measure each unit. We’ll discuss the simplest ones here.

Watts = Amps x Volts

One watt is one ampere of current flowing at the speed of one volt. You can also express this formula as P=VI, Power = Voltage multiplied by Current. So, the power of a 5A and 2V bulb will be 5×2 = 10. That particular bulb will emit 10W of light.

Voltage = Watts/Amps

If you’re even vaguely familiar with mathematics, you must have deduced a way to calculate both voltage and amps based on the first formula. You just need to switch positions. The first formula was W=AxV, the second is V=A/W. Given the example above, we can calculate V=10/5. The result is 2V.

Amps = Watts/Volts

By now, you might’ve figured it out. The formula for calculating amps is A=W/V. If W is 10 and V is 2, then A is 10/2, which equals to 5A.

Ohms = Volts/Amps

As we mentioned before, ohms is the measure of resistance. According to the Ohm’s Law, R (Resistance) = Volts/Amps. So, if the voltage is 2 and the A is 5 then the resistance is 5/2, which equals 2.5 ohms.

There are different ways to calculate voltage, wattage, and resistance. If you want to carry out more complex calculations with more values, you can explore those formulas.

If you want to know more voltage, wattage, and resistance or our custom power products and services, don’t hesitate to contact us at KaRaTec Power Supply Pty. You can give us a call at 612 9808 1127. You can also fill in this contact us form and we’ll reply as soon as possible.

Thanks for reading,
Karatec Power Supply Pty
612 9808 1127

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