Joules to Watt-hours Converter
Convert joules to watt-hours — 3,600 joules make a watt-hour. Results update as you type; exact factors shown.
One joule is 0.0003 watt-hours — see the exact factor, not a rounded rule of thumb.
How the joules to watt-hours 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 |
|---|---|---|
| 1,000 J | 0.2778 Wh | joules to watt-hours |
| 3,600 J | 1 Wh | joules to watt-hours |
| 10,000 J | 2.7778 Wh | joules to watt-hours |
| 36,000 J | 10 Wh | joules to watt-hours |
| 50,000 J | 13.8889 Wh | joules to watt-hours |
| 100,000 J | 27.7778 Wh | joules to watt-hours |
| 360,000 J | 100 Wh | joules to watt-hours |
| 500,000 J | 138.8889 Wh | joules to watt-hours |
| 1,000,000 J | 277.7778 Wh | joules to watt-hours |
| 3,600,000 J | 1,000 Wh | joules to watt-hours |
| 5,000,000 J | 1,388.8889 Wh | joules to watt-hours |
| 10,000,000 J | 2,777.7778 Wh | joules to watt-hours |
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.
Why 3,600?
A watt is a joule per second, and an hour is 3,600 seconds.
What is 1,000,000 J in Wh?
277.8 Wh.
Which unit should I use?
Joules for physics, watt-hours for anything to do with batteries or bills.
What is 3.6 million joules?
One kilowatt-hour.
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.