A watt-hour is 3,600 joules.
Watt-hours to Kilojoules Converter — Wh to kJ
Convert Watt-hour (Wh) to Kilojoule (kJ) using the exact conversion factor (1 watt-hour = 3.6 kilojoule). See the formula, worked examples, conversion table, and common uses.
Watt-hours to Kilojoules converter
Converter
Engineering Converter
Convert common stress, force, torque, power, and energy units used in engineering.
Context values
Some unit families need one extra value for a physically accurate result.
Kilojoule is 1000 joule units.
Result = input x 3600 / 1000.
Energy units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Watt-hours to Kilojoules
Watt-hour and Kilojoule both measure a quantity used in structural or mechanical engineering — commonly stress, pressure, force, torque, power, or energy — where converting between the unit conventions used in different regions, industries, or equipment specifications is a routine part of design work. Watt-hour is most often used for phone, laptop, and power-bank battery capacity ratings.
Formula
kilojoules = watt-hours × 3.6
This factor comes from each unit's defined relationship to the category's base unit: 1 watt-hour equals 3600 base units, and 1 kilojoule equals 1000 base units, so dividing one by the other gives the direct watt-hour-to-kilojoule factor of 3.6.
Simple example
1 Wh × 3.6 = 3.6 kJ
1 watt-hour = 3.6 kilojoules.
Real-world example
100 Wh × 3.6 = 360 kJ
100 watt-hours = 360 kilojoules.
Conversion table
| Watt-hour (Wh) | Kilojoule (kJ) |
|---|---|
| 1 Wh | 3.6 kJ |
| 10 Wh | 36 kJ |
| 50 Wh | 180 kJ |
| 100 Wh | 360 kJ |
| 500 Wh | 1,800 kJ |
| 1,000 Wh | 3,600 kJ |
Reverse conversion: Kilojoule to Watt-hour
3.6 kJ × 0.2777777778 = 1 Wh
3.6 kilojoules = 1 watt-hour.
watt-hours = kilojoules × 0.277777777778
For a page dedicated to this direction, see Kilojoule to Watt-hour.
Understanding the Watt-hour
Watt-hour (Wh) measures energy. The energy delivered by one watt of power sustained for one hour — equal to 3,600 joules. It is classified as a metric derived energy unit.
Where it's used: Universal — standard consumer-electronics and battery energy unit worldwide
Wh vs. kWh. The same unit at different scales: 1,000 Wh equals 1 kWh. Wh suits small consumer-electronics batteries; kWh is used for household electricity billing and larger energy storage.
Uses of the Watt-hour today
- Phone, laptop, and power-bank battery capacity ratings
- Electric-vehicle battery capacity specifications
- Small-scale renewable energy (solar panel) output ratings
Understanding the Kilojoule (kJ)
Kilojoule is 1000 joule units.
Watt-hour — sources
- BIPM SI Brochure — Watt-hour as a common energy unit derived from the coherent SI units watt and second (via the hour).
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many kilojoules are in 1 watt-hour?
1 watt-hour equals 3.6 kilojoules, using the exact defined conversion factor rather than an estimate.
How do I convert watt-hour to kilojoule?
Multiply the watt-hour value by 3.6. The converter above does this instantly to whatever precision you set.
How do I convert kilojoule back to watt-hour?
Use the reverse factor: 1 kilojoule equals 0.2777777778 watt-hours. You can also use the swap control in the converter above to flip the direction instantly.
What is a watt-hour?
Watt-hour (Wh) measures energy. The energy delivered by one watt of power sustained for one hour — equal to 3,600 joules. It is classified as a metric derived energy unit.
What is a kilojoule?
Kilojoule (kJ) is a unit of engineering.
Is the watt-hour to kilojoule conversion exact?
Yes. Both watt-hour and kilojoule are defined by fixed standards rather than physical artifacts, so the factor of 3.6 used above is exact to as many digits as you choose to display.
What is the difference between wh vs. kwh?
The same unit at different scales: 1,000 Wh equals 1 kWh. Wh suits small consumer-electronics batteries; kWh is used for household electricity billing and larger energy storage.
Where is the watt-hour still used today?
Universal — standard consumer-electronics and battery energy unit worldwide