Watt-hour to Joule Converter

Enter the value that you want to convert watt-hour (W/h) to joule (J) or joule to watt-hour.Also written as W/H to J conversion.

1 watt-hour = 3600.0000000 joule

Formula: joule = watt-hour value × 3600.0000000

W/H to J — watt-hour to joule

Value

W/h

Result

36000.00000J

10 watt-hour = 36000.00000 joule

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Watt-hour to Joule: The Essentials

What is Watt-hour?

Watt-hour (W/h) is a unit of energy measurement. 1 watt-hour is equal to 3600.0000000 joule.

The Joule in Engineering

Joule (J) is a unit of energy measurement. 1 joule is equal to 0.0002778 watt-hour.

Energy Units in Different Fields

Energy measurement units reflect their historical origins across different industries. Electrical engineers use kilowatt-hours, nutritionists use calories, physicists use joules, heating engineers use BTUs, and the petroleum industry uses barrels of oil equivalent. Converting between these units is essential for energy auditing, comparing fuel sources, sizing HVAC systems, and understanding electricity bills relative to gas consumption.

watt-hour to joule metric conversion table

0.01 W/h	=	36.00000 J
0.1 W/h	=	360.00000 J
1 W/h	=	3600.00000 J
2 W/h	=	7200.00000 J
3 W/h	=	10800.00000 J
4 W/h	=	14400.00000 J
5 W/h	=	18000.00000 J
6 W/h	=	21600.00000 J
7 W/h	=	25200.00000 J
8 W/h	=	28800.00000 J
9 W/h	=	32400.00000 J
10 W/h	=	36000.00000 J
11 W/h	=	39600.00000 J
12 W/h	=	43200.00000 J
13 W/h	=	46800.00000 J
14 W/h	=	50400.00000 J
15 W/h	=	54000.00000 J
16 W/h	=	57600.00000 J
17 W/h	=	61200.00000 J
18 W/h	=	64800.00000 J

19 W/h	=	68400.00000 J
20 W/h	=	72000.00000 J
30 W/h	=	108000.00000 J
40 W/h	=	144000.00000 J
50 W/h	=	180000.00000 J
60 W/h	=	216000.00000 J
70 W/h	=	252000.00000 J
80 W/h	=	288000.00000 J
90 W/h	=	324000.00000 J
100 W/h	=	360000.00000 J
200 W/h	=	720000.00000 J
300 W/h	=	1080000.00000 J
400 W/h	=	1440000.00000 J
500 W/h	=	1800000.00000 J
600 W/h	=	2160000.00000 J
700 W/h	=	2520000.00000 J
800 W/h	=	2880000.00000 J
900 W/h	=	3240000.00000 J
1000 W/h	=	3600000.00000 J

How to Convert W/H to J (Watt-hour to Joule)?

We can convert watt-hour to joule by using an example.

Example:

Convert 20 Watt-hour to Joule?

We know 1 Watt-hour = 3600.0000000 joule; 1 Joule = 0.0002778 watt-hour.

20 watt-hour = ___J

20 × 3600.0000000 = 72000.00000 J (we know 1 watt-hour = 3600.0000000 joule)

Answer:

20 watt-hour = 72000.00000 joule

How to Convert Watt-Hours to Joules (Step-by-Step)

The watt-hour (Wh) measures energy in portable electronics and small batteries, while the joule is the SI base energy unit. The exact conversion is 1 Wh = 3600 J. This comes from the definition: 1 watt = 1 joule per second, and 1 hour = 3600 seconds.

Identify the energy value in watt-hours (check battery specs or device labels).
Multiply by 3600 to convert to joules.
This follows from: 1 Wh = 1 W × 1 hr = 1 J/s × 3600 s = 3600 J.
Express in kJ for larger values (divide by 1000).

💡 Tip: Battery capacities in mAh can be converted to Wh first (Wh = mAh × V ÷ 1000), then to joules. A 5000 mAh phone at 3.7V = 18.5 Wh = 66,600 J.

Common Wh to Joules Conversions

Reference values for portable electronics and small battery capacities, showing watt-hours converted to joules.

Watt-hour	Joule	Note
1 Wh	3,600 J	Base conversion
5 Wh	18,000 J	Small IoT device battery
18.5 Wh	66,600 J	Typical smartphone battery
50 Wh	180,000 J	Laptop battery (small)
100 Wh	360,000 J	Airline carry-on battery limit
160 Wh	576,000 J	Large laptop battery
500 Wh	1,800,000 J (1.8 MJ)	Portable power station

Solved Examples: Wh to Joules

Question 1: A smartphone battery is rated 18.5 Wh. How many joules does it store?

Solution:

Start with 18.5 Wh.

Multiply by 3600: 18.5 × 3600 = 66,600 J.

In kJ: 66,600 ÷ 1000 = 66.6 kJ.

Answer: 18.5 Wh = 66,600 J = 66.6 kJ

Question 2: A power bank is rated at 74 Wh (20,000 mAh at 3.7V). Express energy in joules.

Solution:

Start with 74 Wh.

Multiply by 3600: 74 × 3600 = 266,400 J.

In kJ: 266,400 ÷ 1000 = 266.4 kJ.

Answer: 74 Wh = 266,400 J = 266.4 kJ

Question 3: An airline limits carry-on batteries to 100 Wh. What is this in joules?

Solution:

Start with 100 Wh.

Multiply by 3600: 100 × 3600 = 360,000 J.

In kJ: 360,000 ÷ 1000 = 360 kJ.

Answer: 100 Wh = 360,000 J = 360 kJ

Question 4: A drone battery holds 45 Wh. Convert to joules.

Solution:

Start with 45 Wh.

Multiply by 3600: 45 × 3600 = 162,000 J.

Answer: 45 Wh = 162,000 J = 162 kJ

Practice: Wh to Joules

Try solving these on your own to test your understanding:

Convert 25 Wh to joules. (Answer: 90,000 J)
A tablet battery holds 30 Wh. Express in kJ. (Answer: 108 kJ)
Convert 200 Wh to joules. (Answer: 720,000 J)
A wireless earbuds case holds 2.5 Wh. Convert to joules. (Answer: 9,000 J)
Convert 80 Wh to joules. (Answer: 288,000 J)

Battery Capacities: mAh vs Wh vs Joules

Batteries are rated in milliamp-hours (mAh) at a given voltage, watt-hours (Wh), or joules. To convert: Wh = mAh × V ÷ 1000, then J = Wh × 3600. Example: iPhone 15 Pro has 3274 mAh at 3.83V = 12.5 Wh = 45,108 J. A MacBook Pro M3 has 72.4 Wh = 260,640 J. Airlines regulate by Wh (100 Wh carry-on limit) because it represents actual stored energy regardless of voltage.

Power Banks and Portable Chargers

Power banks are often marketed in mAh (e.g., 20,000 mAh), but the actual deliverable energy depends on the internal cell voltage (usually 3.6–3.7V). A 20,000 mAh power bank at 3.7V = 74 Wh = 266,400 J. However, due to voltage conversion losses (3.7V internal → 5V USB output), actual deliverable energy is about 60–70% of rated capacity. A 74 Wh bank delivers roughly 45–52 Wh (162,000–187,200 J) of usable charge to your devices.

Why Electronics Use Wh Instead of Joules

Electronics use watt-hours because it connects directly to usage: if a device draws 5 watts, a 50 Wh battery lasts 10 hours (50 ÷ 5 = 10). In joules this would be: 180,000 J ÷ 5 J/s = 36,000 seconds = 10 hours. Same answer, but the Wh calculation is far more intuitive for consumers comparing battery life. The joule remains essential for physics calculations involving force, motion, and heat.

Key Takeaways

Multiply Wh by 3600 to get joules (exact conversion).
1 Wh = 3,600 J = 3.6 kJ — derived from 1 W = 1 J/s and 1 hr = 3600 s.
Smartphone battery (~18 Wh) = ~66,600 J; laptop (~70 Wh) = ~252,000 J.
Airline battery limit: 100 Wh = 360,000 J = 360 kJ.
Convert mAh to Wh first: Wh = mAh × Voltage ÷ 1000, then × 3600 for joules.
Wh is practical for battery life estimates; joules for physics calculations.

Watt-hour to Joule Conversion Formula

joule = watt-hour × 3600.0000000

1 watt-hour = 3600.0000000 joule

1 joule = 0.0002778 watt-hour

Reverse: watt-hour = joule × 0.0002778

Frequently Asked Questions

How many joule are in 1 watt-hour?

There are 3600.0000000 joule in 1 watt-hour. To convert watt-hour to joule, multiply the value by 3600.0000000.

How do I convert watt-hour to joule?

Multiply your watt-hour value by 3600.0000000 to get the equivalent in joule. For example, 5 watt-hour = 5 × 3600.0000000 = 18000.00000 joule.

How do I convert joule to watt-hour?

Multiply your joule value by 0.0002778 to get the equivalent in watt-hour. Alternatively, divide by 3600.0000000.

What is 10 watt-hour in joule?

10 watt-hour is equal to 36000.00000 joule.

What is 100 watt-hour in joule?

100 watt-hour is equal to 360000.00000 joule.