Joules to Watts Converter

Use this converter to easily convert between Joules and Watts. Also supports KiloJoules (KJ), MegaJoules (MJ), MilliWatts (mW), KiloWatts (KW), and MegaWatts (MW).

Share converter:

Embed this tool!
get code     

How many Joules equal one Watt?

Exactly 1 Joules per second equal one Watt. This comes from the definition of the Watt, which is a unit of power used to quantify the rate of energy transfer. In the International System of Units (SI) it is defined as a derived unit of 1 Joule per second [1] with a symbol W. The formula for calculating Power in Watts (W) is:

P(W) = E(J) / t(s)

where P is the power in Watts, E is the energy in Joules and t is the time in seconds. Sometimes it is used to get a result in Watt hours (Wh), so if you know how many Joules per second, you need to divide by 3600 (60 minutes x 60 seconds) to get the Watt hours. Our Joules to Watts converter also supports conversion from KiloJoules (kJ) and MegaJoules (mJ) per second, per minute or per hour to MilliWatts (mW), Watts (W), KiloWatts (KW), and MegaWatts (MW).

Difference between Joules and Watts

Joules are units of energy while Watts are units of power, but there is often confusion about the difference between the terms power and energy. Power is the rate of delivery of energy - work performed per unit of time. On the other hand, energy is the work performed over a period of time. The equivalent energy unit for Joules is Watt hours.

A higher level of power results in more energy used in a given time-frame, therefore, for a set power level, a longer period results in higher energy consumption, while a higher level of power would exhaust the available energy in less time.

How to convert Joules to Watts

In order to convert Joules, which is a unit of energy, to Watts - a unit of power, we need to know a third variable - the time period of interest. Therefore, in our Joules to Watts converter you have two inputs: one for energy (J, KJ, MJ) and one for time (sec, min, hours).

Then you need to follow the definition the Watt as 1 Joule per second and perform the mathematical transformation that are required to convert the time units to seconds and the energy unit to Joules. For example, if your input is in MegaJoules, you need to divide by 1,000,000 in order to get the result in Watts.

Joules to Watts conversion example

Sample task: convert 100 Joules, expended over an hour to Watts. Solution:

J per hour / 3600 = Watts
100 J per hour / 3,600 = 0.027778 Watts
End result:
100 J per hour is equal to 0.027778 Watts

Joules per second to Watts conversion table

J to W conversion table
1 J 1 W
2 J 2 W
3 J 3 W
4 J 4 W
5 J 5 W
6 J 6 W
7 J 7 W
8 J 8 W
9 J 9 W
10 J 10 W
20 J 20 W
30 J 30 W
40 J 40 W
50 J 50 W
60 J 60 W
70 J 70 W
80 J 80 W
90 J 90 W
100 J 100 W
200 J 200 W
300 J 300 W
400 J 400 W
500 J 500 W
600 J 600 W
700 J 700 W
800 J 800 W
900 J 900 W
1,000 J 1,000 W


[1] NIST Special Publication 330 (2008) - "The International System of Units (SI)", edited by Barry N.Taylor and Ambler Thompson

[2] International Organization for Standardization (1993). ISO Standards Handbook: Quantities and units (3rd edition). Geneva: ISO. ISBN 92-67-10185-4.

Cite this converter & page

If you'd like to cite this online converter resource and information as provided on the page, you can use the following citation:
Georgiev G.Z., "Joules to Watts Converter", [online] Available at: URL [Accessed Date: 12 Jun, 2021].