The kilojoule
The kilojoule (kJ) equals exactly 1,000 joules. It is the standard unit on EU and many non-US nutrition labels — 1 dietary calorie ≈ 4.184 kJ. It also appears in industrial-process specifications and energy-storage ratings.
Kilojoules to Watt-hours Converter
1 kJ = 0.277778 Wh (kilojoule → watt-hour)
1 kJ = 0.277778 Wh
1 kilojoule equals 0.277778 watt-hours. To convert kilojoules to watt-hours, multiply the kilojoule value by 0.277778. For quick reference: 1 kJ = 0.277778 Wh, 5 kJ = 1.38889 Wh, 10 kJ = 2.77778 Wh, 100 kJ = 27.7778 Wh.
Formula
Watt-hours = Kilojoules × 0.277778Quick
When to use kilojoules → watt-hours
Kilojoules to watt-hours divides by 3.6 exactly (1 Wh = 3,600 J = 3.6 kJ). A laptop battery storing 250 kJ holds 69.4 Wh — consistent with the 50–100 Wh ratings printed on airline-approved batteries. The conversion links thermodynamic or nutritional figures (kJ) to electrical-storage figures (Wh). Airlines limit carry-on batteries by watt-hours, so if your pack's label only shows kJ, this ÷3.6 step is exactly the check security applies.
Induction-hob energy ratings are sometimes quoted in kilojoules per cooking cycle in appliance testing standards, but the figure that matters for a household energy bill is watt-hours. A 3,600 kJ cooking cycle uses exactly 1,000 Wh, or 1 kWh; a quick 720 kJ reheat cycle uses 200.0 Wh. Because 1 Wh is defined as 3,600 J, this conversion divides by exactly 3.6 after the kJ-to-J step, and appliance testers keep the intermediate kJ figure for efficiency work while reporting the consumer-facing number in Wh.
How to convert kilojoules to watt-hours
Take your value
Start with your value in kilojoules.
Multiply by 0.277778
Multiply the kilojoule value by 0.277778. This is the exact conversion factor from kilojoules to watt-hours.
Read the result
The product is your value in watt-hours. For example, 5 kJ × 0.277778 = 1.38889 Wh.
Conversion formula
The exact factor from kilojoules to watt-hours is 0.277778.
Watt-hours = Kilojoules × 0.277778
Kilojoules to Watt-hours conversion table
Fifty common reference values, hand-picked for skim utility. Use the calculator above for any value not listed.
| Kilojoules (kJ) | Watt-hours (Wh) |
|---|---|
| 0.001 kJ | 0.00027778 Wh |
| 0.01 kJ | 0.0027778 Wh |
| 0.1 kJ | 0.027778 Wh |
| 0.5 kJ | 0.13889 Wh |
| 1 kJ | 0.27778 Wh |
| 1.5 kJ | 0.41667 Wh |
| 2 kJ | 0.55556 Wh |
| 5 kJ | 1.3889 Wh |
| 10 kJ | 2.7778 Wh |
| 20 kJ | 5.5556 Wh |
| 50 kJ | 13.889 Wh |
| 100 kJ | 27.778 Wh |
| 200 kJ | 55.556 Wh |
| 250 kJ | 69.444 Wh |
| 500 kJ | 138.89 Wh |
| 1000 kJ | 277.78 Wh |
| 2000 kJ | 555.56 Wh |
| 2500 kJ | 694.44 Wh |
| 3600 kJ | 1000 Wh |
| 5000 kJ | 1388.9 Wh |
| 7500 kJ | 2083.3 Wh |
| 10000 kJ | 2777.8 Wh |
| 25000 kJ | 6944.4 Wh |
| 50000 kJ | 13889 Wh |
| 100000 kJ | 27778 Wh |
| 250000 kJ | 69444 Wh |
| 500000 kJ | 138889 Wh |
| 1000000 kJ | 277778 Wh |
| 2000000 kJ | 555556 Wh |
| 3600000 kJ | 1000000 Wh |
| 5000000 kJ | 1388889 Wh |
| 10000000 kJ | 2777778 Wh |
| 25000000 kJ | 6944444 Wh |
| 50000000 kJ | 13888889 Wh |
| 100000000 kJ | 27777778 Wh |
| 250000000 kJ | 69444444 Wh |
| 500000000 kJ | 138888889 Wh |
| 1000000000 kJ | 277777778 Wh |
| 2000000000 kJ | 555555556 Wh |
| 5000000000 kJ | 1388888889 Wh |
| 10000000000 kJ | 2777777778 Wh |
| 20000000000 kJ | 5555555556 Wh |
| 50000000000 kJ | 13888888889 Wh |
| 100000000000 kJ | 27777777778 Wh |
| 1000000000000 kJ | 277777777778 Wh |
| 10000000000000 kJ | 2777777777778 Wh |
| 100000000000000 kJ | 27777777777778 Wh |
| 1000000000000000 kJ | 277777777777778 Wh |
| 10000000000000000 kJ | 2.7778 × 10^15 Wh |
| 100000000000000000 kJ | 2.7778 × 10^16 Wh |
Real-world reference
A medium banana provides about 450 kJ of food energy. A laptop battery typically stores 200–300 kJ. In watt-hours, that gives you: 1 kJ = 0.277778 Wh, 10 kJ = 2.77778 Wh, 100 kJ = 27.7778 Wh.
Frequently asked questions
- How many watt-hours are in 1 kilojoule?
- 1 kilojoule equals 0.277778 watt-hours.
- How do I convert kilojoules to watt-hours?
- Multiply the kilojoule value by 0.277778. So x kJ × 0.277778 = the equivalent in Wh.
- What is 5 kilojoules in watt-hours?
- 5 kilojoules equals 1.38889 watt-hours.
- What is 10 kilojoules in watt-hours?
- 10 kilojoules equals 2.77778 watt-hours.
- What is 100 kilojoules in watt-hours?
- 100 kilojoules equals 27.7778 watt-hours.
- How do I convert back from watt-hours to kilojoules?
- Multiply the watt-hour value by 3.6. For example, 1 Wh = 3.6 kJ.
- Is the kilojoule bigger than the watt-hour?
- No. 1 kilojoule is smaller than 1 watt-hour. It takes 3.6 kilojoules to equal 1 watt-hour.
- Are these conversion factors exact?
- The factor is derived directly from the SI definitions of kilojoule and watt-hour; the displayed value is rounded for readability, and the browser computes using IEEE 754 double-precision arithmetic.
About the kilojoule and the watt-hour
The watt-hour
The watt-hour (Wh) equals 3,600 joules — the energy delivered by one watt of power over one hour. It is the natural unit for batteries, small electronics, and short-duration electrical loads.