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Joules to Watts Calculator

Power is energy divided by time. Enter the joules and how long the energy took to deliver, from milliseconds to hours, and get the power in watts. Type in the watts box to go the other way.

Last updated: October 24, 2026

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WattsTo

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Step-by-step calculation

How to use the Joules to Watts Calculator

Enter the energy in joules.
Set the time and pick its unit: milliseconds, seconds, minutes or hours.
Read the power in watts, plus kW, horsepower and more.
Need joules from watts? Type in the Watts box or press ⇄.
Check the steps, then press Copy result.

Joules to watts formula

P (W) = E (J) ÷ t (s)

Take the energy in joules.
Convert the time to seconds (1 ms = 0.001 s, 1 min = 60 s, 1 h = 3,600 s).
Divide energy by time. One watt is exactly one joule per second.

Worked example: an electric kettle delivers 72,000 J of heat in 1 minute. Time = 60 s, so P = 72,000 ÷ 60 = 1,200 W (1.2 kW).

Short pulse example: a camera flash capacitor releases 50 J in 5 ms (0.005 s): 50 ÷ 0.005 = 10,000 W. A small amount of energy released very quickly means a large power.

Reverse formula (watts to joules): E = P × t. Example: a 60 W bulb left on for 10 minutes uses 60 × 600 = 36,000 J.

Joules and watts measure different things: joules are an amount of energy, watts are a rate. You always need a time to convert between them.

Joules to watts table

Values follow the time set in the calculator (2 seconds by default). Click any row to load it.

Joules to watts over 2 s

Joules	Watts
1 J	0.5 W
2 J	1 W
3 J	1.5 W
4 J	2 W
5 J	2.5 W
6 J	3 W
7 J	3.5 W
8 J	4 W
9 J	4.5 W
10 J	5 W
11 J	5.5 W
12 J	6 W
13 J	6.5 W
14 J	7 W
15 J	7.5 W
16 J	8 W
17 J	8.5 W
18 J	9 W
19 J	9.5 W
20 J	10 W
21 J	10.5 W
22 J	11 W
23 J	11.5 W
24 J	12 W
25 J	12.5 W
26 J	13 W
27 J	13.5 W
28 J	14 W
29 J	14.5 W
30 J	15 W
31 J	15.5 W
32 J	16 W
33 J	16.5 W
34 J	17 W
35 J	17.5 W
36 J	18 W
37 J	18.5 W
38 J	19 W
39 J	19.5 W
40 J	20 W
41 J	20.5 W
42 J	21 W
43 J	21.5 W
44 J	22 W
45 J	22.5 W
46 J	23 W
47 J	23.5 W
48 J	24 W
49 J	24.5 W
50 J	25 W
51 J	25.5 W
52 J	26 W
53 J	26.5 W
54 J	27 W
55 J	27.5 W
56 J	28 W
57 J	28.5 W
58 J	29 W
59 J	29.5 W
60 J	30 W
61 J	30.5 W
62 J	31 W
63 J	31.5 W
64 J	32 W
65 J	32.5 W
66 J	33 W
67 J	33.5 W
68 J	34 W
69 J	34.5 W
70 J	35 W
71 J	35.5 W
72 J	36 W
73 J	36.5 W
74 J	37 W
75 J	37.5 W
76 J	38 W
77 J	38.5 W
78 J	39 W
79 J	39.5 W
80 J	40 W
81 J	40.5 W
82 J	41 W
83 J	41.5 W
84 J	42 W
85 J	42.5 W
86 J	43 W
87 J	43.5 W
88 J	44 W
89 J	44.5 W
90 J	45 W
91 J	45.5 W
92 J	46 W
93 J	46.5 W
94 J	47 W
95 J	47.5 W
96 J	48 W
97 J	48.5 W
98 J	49 W
99 J	49.5 W
100 J	50 W

Watts to joules over 2 s

Watts	Joules
1 W	2 J
2 W	4 J
3 W	6 J
4 W	8 J
5 W	10 J
6 W	12 J
7 W	14 J
8 W	16 J
9 W	18 J
10 W	20 J
11 W	22 J
12 W	24 J
13 W	26 J
14 W	28 J
15 W	30 J
16 W	32 J
17 W	34 J
18 W	36 J
19 W	38 J
20 W	40 J
21 W	42 J
22 W	44 J
23 W	46 J
24 W	48 J
25 W	50 J
26 W	52 J
27 W	54 J
28 W	56 J
29 W	58 J
30 W	60 J
31 W	62 J
32 W	64 J
33 W	66 J
34 W	68 J
35 W	70 J
36 W	72 J
37 W	74 J
38 W	76 J
39 W	78 J
40 W	80 J
41 W	82 J
42 W	84 J
43 W	86 J
44 W	88 J
45 W	90 J
46 W	92 J
47 W	94 J
48 W	96 J
49 W	98 J
50 W	100 J
51 W	102 J
52 W	104 J
53 W	106 J
54 W	108 J
55 W	110 J
56 W	112 J
57 W	114 J
58 W	116 J
59 W	118 J
60 W	120 J
61 W	122 J
62 W	124 J
63 W	126 J
64 W	128 J
65 W	130 J
66 W	132 J
67 W	134 J
68 W	136 J
69 W	138 J
70 W	140 J
71 W	142 J
72 W	144 J
73 W	146 J
74 W	148 J
75 W	150 J
76 W	152 J
77 W	154 J
78 W	156 J
79 W	158 J
80 W	160 J
81 W	162 J
82 W	164 J
83 W	166 J
84 W	168 J
85 W	170 J
86 W	172 J
87 W	174 J
88 W	176 J
89 W	178 J
90 W	180 J
91 W	182 J
92 W	184 J
93 W	186 J
94 W	188 J
95 W	190 J
96 W	192 J
97 W	194 J
98 W	196 J
99 W	198 J
100 W	200 J

Common values over 2 s

Joules	Watts	Example
1 J	0.5 W	1 joule
100 J	50 W	≈ lifting 10 kg up 1 m
1,000 J	500 W	1 kilojoule
1,055.06 J	527.53 W	1 BTU
3,600 J	1,800 W	1 watt-hour
4,184 J	2,092 W	1 kilocalorie (food Calorie)
1,000,000 J	500,000 W	1 megajoule
3,600,000 J	1,800,000 W	1 kilowatt-hour

Energy and power units at a glance

Unit	In joules	What it measures
1 watt-second (W·s)	1 J	Energy
1 calorie (cal)	4.184 J	Energy
1 BTU	1,055.06 J	Energy
1 watt-hour (Wh)	3,600 J	Energy
1 kilocalorie (kcal)	4,184 J	Energy
1 kilowatt-hour (kWh)	3,600,000 J	Energy
1 watt (W)	1 J every second	Power
1 horsepower (hp)	745.7 J every second	Power

Tip: if you know power and want energy, multiply by time in seconds. If your energy is in kWh and your time in hours, you can skip joules entirely: kW = kWh ÷ hours.

Frequently asked questions

How do you convert joules to watts?

Divide the energy in joules by the time in seconds: P = E ÷ t. For example, 1,000 J delivered in 2 seconds is 500 W.

Is a joule the same as a watt?

No. A joule is an amount of energy and a watt is a rate of energy use. One watt equals one joule per second, so 1 J delivered in 1 second is 1 W.

Can I convert joules to watts without time?

No. Without a time duration the conversion is impossible, because the same energy delivered faster means more power.

How many watts is 1 joule per second?

Exactly 1 watt. 1 joule per millisecond is 1,000 W, and 1 joule per minute is about 0.0167 W.

How do I convert watts to joules?

Multiply watts by the time in seconds: E = P × t. A 100 W device running for 1 minute uses 100 × 60 = 6,000 J.

How many joules are in a kilowatt-hour?

One kWh equals 3,600,000 joules (3.6 MJ), because 1 kW is 1,000 J per second and an hour has 3,600 seconds.

Are all the tools on FreeToolCabin tested for quality and accuracy?

Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.

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