Watt-Hours to Joules Converter
Convert watt-hours to joules — one watt-hour is exactly 3,600 J. Results update as you type; exact factors shown.
One watt-hour is 3,600 joules — see the exact factor, not a rounded rule of thumb.
How the watt-hours to joules converter works
Energy converts through the joule. A thermochemical calorie is exactly 4.184 J, so a food Calorie (kcal) is 4.184 kJ. A kilowatt-hour is exactly 3.6 MJ. A BTU is 1,055.056 J and a US therm is 100,000 BTU.
The UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
Common energy conversions
| From | To | Units |
|---|---|---|
| 0.5 Wh | 1,800 J | watt-hours to joules |
| 1 Wh | 3,600 J | watt-hour to joules |
| 2 Wh | 7,200 J | watt-hours to joules |
| 5 Wh | 18,000 J | watt-hours to joules |
| 10 Wh | 36,000 J | watt-hours to joules |
| 20 Wh | 72,000 J | watt-hours to joules |
| 50 Wh | 180,000 J | watt-hours to joules |
| 100 Wh | 360,000 J | watt-hours to joules |
| 250 Wh | 900,000 J | watt-hours to joules |
| 500 Wh | 1,800,000 J | watt-hours to joules |
| 1,000 Wh | 3,600,000 J | watt-hours to joules |
| 5,000 Wh | 18,000,000 J | watt-hours to joules |
Units in this converter and their exact factors
| Unit | Symbol | One unit in joules |
|---|---|---|
| joule | J | 1 joule |
| kilojoule | kJ | 1,000 joule |
| megajoule | MJ | 1,000,000 joule |
| calorie (thermochemical) | cal | 4.184 joule |
| kilocalorie (food Calorie) | kcal | 4,184 joule |
| watt-hour | Wh | 3,600 joule |
| kilowatt-hour | kWh | 3,600,000 joule |
| British thermal unit | BTU | 1,055.05585262 joule |
| therm (US) | thm | 105,505,585.262 joule |
| foot-pound | ft·lb | 1.3558179483 joule |
FAQFrequently asked questions about energy conversion
How many joules in a watt-hour?
Exactly 3,600, because a watt is a joule per second and an hour is 3,600 seconds.
What is 1 kWh in joules?
3.6 million J, or 3.6 MJ.
Why does electricity bill in watt-hours?
Because it is power times time, which is what a meter actually accumulates.
What is a phone battery?
Around 15 Wh, which is 54,000 J.
What is 100 Wh?
360,000 J — the airline cabin-baggage battery limit.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.