Convert Watt-hours (Wh) to Kilojoules (kJ)

1 Wh = 3.6 kJ

How many Kilojoules in a Watt-hour?Printable chart →

Converting energy from Watt-hours (Wh) to Kilojoules (kJ) is essential for understanding energy consumption. The conversion factor is simple: 1 Wh equals 3.6 kJ, making it easy to switch between these two units depending on your needs.

Watt-hour (Wh)

Kilojoule (kJ)

3.6

≈ 3 19/32 kJ

Conversion Formula

kJ = Wh × 3.6

Reverse: Wh = kJ × 0.277778

Quick mental math: To estimate quickly, remember that 1 Wh is roughly 3.6 kJ, so just multiply by 3.6.

Conversion Examples

1 Wh × 3.6 =

3.6 kJ

1 Watt-hours = 3.6 Kilojoules

5 Wh × 3.6 =

18 kJ

5 Watt-hours = 18 Kilojoules

10 Wh × 3.6 =

36 kJ

10 Watt-hours = 36 Kilojoules

25 Wh × 3.6 =

90 kJ

25 Watt-hours = 90 Kilojoules

50 Wh × 3.6 =

180 kJ

50 Watt-hours = 180 Kilojoules

100 Wh × 3.6 =

360 kJ

100 Watt-hours = 360 Kilojoules

Watt-hour to Kilojoule Table

Quick convert your value:

Wh =—kJ

Start:Step:Rows:Precision:

Watt-hour (Wh)	Kilojoule (kJ)	Fraction
1	3.6	3 19/32
2	7.2	7 13/64
3	10.8	10 51/64
4	14.4	14 13/32
5	18	—
6	21.6	21 19/32
7	25.2	25 13/64
8	28.8	28 51/64
9	32.4	32 13/32
10	36	—
11	39.6	39 19/32
12	43.2	43 13/64
13	46.8	46 51/64
14	50.4	50 13/32
15	54	—
16	57.6	57 19/32
17	61.2	61 13/64
18	64.8	64 51/64
19	68.4	68 13/32
20	72	—

Unit Definitions

What is a Watt-hour (Wh)?

Metric (SI)Worldwide

A Watt-hour (Wh) is a unit of energy representing one watt of power used for one hour.

History

The Watt-hour was introduced in the late 19th century as electric power began to be commercially distributed. It became crucial for measuring energy consumption in electrical devices.

Current Use

Today, the watt-hour is commonly used in household appliances, battery capacities, and electrical billing.

Learn more about Watt-hour

What is a Kilojoule (kJ)?

Metric (SI)Worldwide

A Kilojoule (kJ) is a metric unit of energy equivalent to 1,000 joules.

History

The joule was named after the English physicist James Prescott Joule in the 19th century. The kilojoule became a standard unit as scientific measurement systems evolved.

Current Use

Kilojoules are widely used in nutrition to express the energy content of food and in various scientific applications.

Learn more about Kilojoule

Frequently Asked Questions

How much energy does a 100W light bulb use in kJ after 5 hours?

To find out how much energy a 100W light bulb uses in 5 hours, first calculate the watt-hours: 100W * 5h = 500 Wh. Then, convert that to kilojoules using the conversion factor: 500 Wh * 3.6 kJ/Wh = 1800 kJ. So, a 100W light bulb consumes 1800 kJ of energy over 5 hours.

What is the energy consumption of a laptop in kJ after 3 hours of use?

If your laptop consumes 60W, then in 3 hours, it will use 60W * 3h = 180 Wh. Converting that to kilojoules gives you 180 Wh * 3.6 kJ/Wh = 648 kJ. Therefore, using a laptop for 3 hours at 60W consumes 648 kJ of energy.

How can I calculate the energy used by a microwave in kJ during a 10-minute cooking session?

If your microwave operates at 800W and you use it for 10 minutes (which is 1/6 of an hour), you calculate the watt-hours as follows: 800W * (10/60)h = 133.33 Wh. Converting that to kilojoules, 133.33 Wh * 3.6 kJ/Wh = 480 kJ. Thus, cooking in a microwave for 10 minutes at 800W uses approximately 480 kJ of energy.

What is the energy cost in kJ for charging a smartphone for 2 hours?

Assuming your smartphone charger outputs 5W, you would calculate the energy used in watt-hours as 5W * 2h = 10 Wh. To convert this to kilojoules, you multiply by the conversion factor: 10 Wh * 3.6 kJ/Wh = 36 kJ. Therefore, charging a smartphone for 2 hours at 5W consumes 36 kJ of energy.

How much energy is consumed when running a treadmill for 30 minutes at 150W?

If you run on a treadmill that uses 150W for 30 minutes, first convert the time to hours: 30 minutes is 0.5 hours. The energy consumption in watt-hours is 150W * 0.5h = 75 Wh. Converting to kilojoules gives 75 Wh * 3.6 kJ/Wh = 270 kJ. Thus, running on a treadmill at 150W for 30 minutes uses 270 kJ of energy.

Popular Energy Conversions

Kilowatt to HorsepowerkW → HP Calorie to Kilocaloriecal → kcal Joule to CalorieJ → cal Kilowatt-hour to BTUkWh → BTU BTU to JouleBTU → J Kilocalorie to Joulekcal → J

Convert Watt-hour to Other Units

Watt-hour to Joule→ J Watt-hour to Kilojoule→ kJ Watt-hour to Calorie→ cal Watt-hour to Kilocalorie→ kcal Watt-hour to Joule→ J Watt-hour to Calorie→ cal Watt-hour to Kilocalorie→ kcal Watt-hour to Kilowatt-hour→ kWh

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Joule to KilojouleJ → kJ Joule to Watt-hourJ → Wh Kilojoule to JoulekJ → J Kilojoule to CaloriekJ → cal Kilojoule to KilocaloriekJ → kcal