Created By : awnish

Reviewed By : Phani Ponnapalli

Last Updated : Apr 10, 2023

Our free Watt Calculator is one of the best tools that help to find the power, current, and resistance. Simply you have to provide the required data such as resistance, the voltage in the fields of the calculator and click on the calculate button. At the output section, you can see power and current as soon as possible.

Choose a Calculation:
Current (I):

Steps to Find Watt, Amps

Below provided are the steps to calculate the watts, amps, ohms in a circuit. Go through these rules and follow them to check the power value easily.

  • Obtain resistance and voltage values.
  • Divide voltage by resistance to get the current.
  • Multiply the voltage and current to check the power value in Watt.

Watt's Equation and Ohm's Law

A Watt is defined as the unit of power. It is the rate of work when a current of one ampere flows through a conductor which has an electrical potential difference of one volt.

1W = 1V x 1A

Watt's Equation

In an electrical circuit, a watt is stated as the product of volt and amp.

P = V x I

Ohm's Law

Ohm's law states that the voltage across the conductor is proportional to the current flowing through it.

V = I x R

The terms of volts, amps, ohms and watt is provided here.

  • Power is the rate of transferring electrical energy per unit of time. Its unit is the watt.
  • Voltage is the potential difference between two points of a conductor. Its unit is volt.
  • Current is the measure of the amount of electrons passing through any point of the conductor per unit of time. Its unit is ampere.
  • Resistance is the strength of the wire to the opposite of the electrons flow. Its unit is the ohm.

The different formulas to calculate the power, voltage, electric current and resistance are along the lines:

  1. Resistance:
    • R = V/I
    • R = V²/P
    • R = P/I²
  2. Voltage:
    • V = I x R
    • V = P/I
    • V = √(P x R)
  3. Electric Current:
    • I = V/R
    • I = P/V
    • I = √(P/R)
  4. Power:
    • P = V x I
    • P = V²/R
    • P = I² x R


R is the resistance

I is the current

P is the power

V is the voltage


Question: If 120 Watt light bulb with 150 volts of electrical potential, then find the current and resistance of the bulb?


Given that

Voltage V = 150 V

Power P = 120 W

Current I = P/V

I = 120/150

= 0.8 A

Resistance R = V/I

R = 150/0.8

R = 187.5 Ω

Therefore, the current and resistance is 0.8 A, 187.5 Ω.

Explore more physics concepts from our site Physicscalc.Com by using our free online calculators and also make your calculations easy during homework.

Frequently Asked Questions on Watt Calculator

1. How to calculate Watts?

The simple formulas to find the power generated in a circuit is P = V x I or P = V²/R or P = I² x R. You have to substitute the values in the respective formula. And do the math operations to obtain the watt value easily.

2. How do I use Watt Calculator to find ohms and amps?

Just provide the known values i.e voltage and power details in the calculator fields and hit the blue colour calculate button to check the resistance and current values in the output field in a less amount of time.

3. What is meant by Watt?

Watt is defined as the rate of work. In a mathematical way, when one ampere of current flows through a wire and that has one volt as voltage.

4. What is the relation between watt and volt?

The relation between watt and volt is 1 volt = 1 watt/1 ampere. Watt is the SI unit of power and voltage is the unit of potential difference. Volt can be measured by using a voltmeter and watt can be measured using a power meter.