Kilojoules to Watt Hours
Convert kilojoules to watt hours instantly — one kilojoule is 0.277778 watt hours.
| Kilojoules | Watt Hours |
|---|---|
| 1 kJ | 0.277778 Wh |
| 2 kJ | 0.555556 Wh |
| 3 kJ | 0.833333 Wh |
| 5 kJ | 1.388889 Wh |
| 10 kJ | 2.777778 Wh |
| 25 kJ | 6.944444 Wh |
| 50 kJ | 13.888889 Wh |
| 100 kJ | 27.777778 Wh |
How to use
- Enter a value in the Kilojoules field.
- The Watt Hours figure appears immediately — no button to press.
- Typing in the Watt Hours field converts back to Kilojoules the same way.
- Use the reference table for the values that come up most often.
Kilojoules to Watt Hours formula
To convert kilojoules to watt hours, multiply by 0.277777778.
Wh = kJ × 0.277777778
Put another way, one kilojoule is exactly 5/18 watt hours.
Why this factor: the kilojoule and the watt-hour are both defined against the joule, so dividing one definition by the other gives 0.277777778 directly. Both definitions are set out in full below.
To go the other way, divide by 0.277777778 — or use the Watt Hours to Kilojoules converter, which is the same calculation reversed.
Worked example
Given 2000 kJ, multiplying by 0.277777778 yields 555.555556 Wh.
2000 kJ × 0.277777778 = 555.555556 Wh
The converter above does this for any value you type, in either direction.
What is a kilojoule?
A kilojoule is 1,000 joules, the metric unit of food energy.
Definition: Exactly 1,000 joules.
Where it is used: Nutrition labels in Europe and Australia, and heating and cooling loads.
What is a watt-hour?
A watt-hour is the energy delivered by one watt of power sustained for one hour.
Definition: Exactly 3,600 joules.
Where it is used: Battery capacity for laptops, e-bikes and power tools, and small-scale energy metering.
Worth knowing: Airline lithium-battery limits are set in watt-hours, which is why laptop and power-bank capacities are labelled in Wh.
Kilojoules vs Watt Hours
The kilojoule is a metric unit while the watt-hour is a specialized unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many watt hours are in a kilojoule?
One kilojoule equals 0.277777778 watt hours.
What is the formula to convert kilojoules to watt hours?
Multiply the number of kilojoules by 0.277777778. To reverse it, divide by 0.277777778 instead.
How do I convert watt hours back to kilojoules?
Divide by 0.277777778, which is the same as multiplying by 3.6.
How many watt hours are in 10 kilojoules?
10 kJ works out to 2.777778 Wh.
Is there anything to watch out for with watt hours?
Airline lithium-battery limits are set in watt-hours, which is why laptop and power-bank capacities are labelled in Wh.
How is the kilojoule defined?
Exactly 1,000 joules.