Convert joules to watt-hours

1 J=0.0002778Wh

Use the converter below to change any joules value into watt-hours instantly — with formula, conversion table, and real-world examples.

You have

Equals

0.00027778

Conversion formula

Forward

watt-hours = joules × 0.0002778

Reverse

joules = watt-hours × 3,600

Example: 10 J × 0.0002778 = 0.002778 Wh.

About both units

From

Joule

The joule is the SI unit of energy, work and heat. Defined as one newton-metre or one watt-second. Named after James Prescott Joule who demonstrated the mechanical equivalent of heat. Lifting a 100 g apple 1 metre requires about 1 J.

Real-world: Lifting a 100 g apple 1 m: ≈ 1 J. 100 kcal snack: 418,400 J. Hand grenade: ~650 kJ.

Read full joule reference →

Watt-Hour

The watt-hour equals 3600 joules — 1 W delivered for 1 hour. Used for phone, laptop and small-battery capacities. A typical smartphone battery is 10–20 Wh; a laptop is 50–100 Wh.

Real-world: iPhone battery: 12 Wh. MacBook Pro: 70 Wh. Power bank: 20 Wh–100 Wh. Airplane carry-on limit: usually 100 Wh.

Read full watt-hour reference →

Joule to Watt-Hour conversion table

Common joules to watt-hours values for quick reference.

Joule (J)	Watt-Hour (Wh)
1 J	0.0002778 Wh
10 J	0.002778 Wh
100 J	0.02778 Wh
500 J	0.1389 Wh
1,000 J	0.2778 Wh
5,000 J	1.38889 Wh
10,000 J	2.77778 Wh
50,000 J	13.8889 Wh
100,000 J	27.7778 Wh
500,000 J	138.889 Wh

Tips & common mistakes

Quick tips

1 J = 1 N·m = 1 W·s.
1 kWh = 3,600,000 J (3.6 MJ).
For nutrition 1 kcal = 4.184 kJ.

Avoid these

Confusing joule (energy) with newton (force).
Mixing joule with watt — watt is joule per second.
Using kJ when labels call for kcal on US nutrition.

Frequently asked questions

How many watt-hours in a joule?

One joule equals 0.0002778 watt-hours.

How do I convert joules to watt-hours?

Multiply the joule value by 0.0002778 to get the equivalent in watt-hours.

What is 100 joules in watt-hours?

100 joules equals 0.02778 watt-hours.

Is a joule bigger than a watt-hour?

No. 1 joule equals 0.0002778 watt-hours, so one joule is smaller.

How to convert joules to watt-hours without a calculator?

Multiply by 0 for a quick estimate; use a calculator for precise results.

Related energy conversions

📊 See full comparison matrix →

Conversions in other categories

WeightKilogram → Pound LengthKilometer → Mile TemperatureCelsius → Fahrenheit VolumeLiter → US Gallon AreaSquare Meter → Square Foot SpeedKilometer per Hour → Mile per Hour PressureBar → Pound per Square Inch PowerKilowatt → Mechanical Horsepower