How to Calculate Watts

The amount of power drawn by a household appliance is given in watts. Here's how to calculate wattage.

Step 1: Understand the definition
Know that 1 watt is the amount of power produced by a current of 1 ampere across a potential difference of 1 volt.

Tip
Equivalently 1 watt is the amount of work done at the rate of one joule per second.

Step 2: Understand appliances
Understand that the wattage listed on an appliance is the maximum power it draws. Because many appliances have a range of settings, the actual amount of power consumed at any given time depends on the setting used.

Step 3: Use a formula
Consider using a formula to estimate wattage. To do this you will need to know the current draw, the voltage used by the appliance, and/or the resistance of the appliance.

Step 4: Use voltage and current
Calculate the wattage from the product of voltage and the current for the appliance. Voltage is measured in volts and current in amperes (or amps).

Tip
If an appliance is rated at 5 amps and 120 volts, the wattage is 600 watts (5 amps times 120 volts, which equals 600 watts).

Step 5: Use current and resistance
Obtain the wattage as the product of the square of current times the resistance. Resistance is measured in ohms.

Step 6: Use voltage and resistance
Calculate the wattage from the quotient of the square of voltage divided by resistance.

Did You Know?
James Watt was an 18th-century mechanical engineer who made important contributions to improvements of the steam engine.

[brd]

The cooker lid just opened. Should calculate steam power inside cooker.

[tedlahm]

Question please. The neutral conductor connected to a GFCI (white) is always
insulated. Why is the EXACT SAME neutral conductor that runs from outside
the home to the STEP DOWN TRANSFORMER not insulated?

[jesse]

It would be helpful if you translated the appliance label to the formulas

[mangreat]

Can a 1000 watt inverter power something that takes 240 volts. And how many volts is in 1000 watts ???

[morilollen]

the power rating of a 2 kilo ohms resistance is 80 watt. calculate the maximum permisible current which can flow through it.

[chelseaFC]

This is not teaching. Just providing answers without the knowledge

[gorernest]

my dryer120/240VAC-60HZ-24AMPS
my washing machine 120v-60HZ-9AMPS
can anyone tell me the result?
thanks :D

[arvin]

So I have an electric kettle and here's what I saw
220v-240v
50/60hz
350w
How to get the Amp? Or it is impossible?

[ANFIEE]

... So, is there any chance that you could translate this to Norwegian? :)

[ivanmichaeloro]

How to know the volts if the amout is 1400w

[mikefromflorida]

Surely you can explain this without needless music playing in the background.
When do you intentionally turn on music just before you start talking to someone so they must listen to that while you speak? Answer - never, because that would be rude, and the other person would ask you why the hell you just did such a thing.

[gamesmoney]

I have no idea what this random lady is talking about

[jeram]

calculate for me .... input 100-240V -50/60Hz 0.6A
output 5V --- 4A