Joules (J) to Watt-hours (W·h) Conversion
Joules
The joule (J) is the SI derived unit of energy, work, and heat, defined as the work done when a force of one newton displaces an object by one metre (J = N·m = kg·m²·s⁻²). Named after James Prescott Joule, who established the mechanical equivalent of heat in the 1840s, the joule unifies all forms of energy — mechanical, thermal, electrical, chemical, and nuclear — under one framework. One joule is small: lifting an apple (≈100 g) one metre requires about 1 joule, while a human at rest metabolises approximately 80 joules per second.
Watt-hours
The watt-hour (W·h) is a unit of energy equal to exactly 3,600 joules, defined as the energy consumed by a one-watt device operating for one hour. It is used in electrical engineering and consumer electronics for expressing battery capacities: a smartphone battery typically holds 10–20 Wh. In aviation, aircraft battery capacities are specified in watt-hours for international transport regulations (lithium batteries above 100 Wh face restrictions).
| Joules (J) | Watt-hours (W·h) |
|---|---|
| 0.1 J | 0.0000278 W·h |
| 1 J | 0.000278 W·h |
| 2 J | 0.000556 W·h |
| 3 J | 0.000833 W·h |
| 5 J | 0.00139 W·h |
| 10 J | 0.00278 W·h |
| 20 J | 0.00556 W·h |
| 30 J | 0.00833 W·h |
| 50 J | 0.0139 W·h |
| 100 J | 0.0278 W·h |
| 1000 J | 0.2778 W·h |
Frequently Asked Questions (FAQ)
How many watt-hours are in 1 joules?
1 joules (J) is exactly 0.000278 watt-hours (W·h).
How do I convert joules to watt-hours?
Multiply the value in joules by 0.000278 to get the result in watt-hours. Or use the converter above — type any number and see the result instantly.