Convert energy units — joules, calories, kilowatt-hours, BTU, kilojoules.
| Unit | Name | Value |
|---|---|---|
| J | Joule | 1000 |
| cal | Calorie | 239.00574 |
| kcal | Kilocalorie (Cal) | 0.23900574 |
| kWh | Kilowatt-hour | 0.00027777778 |
| BTU | BTU | 0.94781339 |
Formula: Kilowatt-Hour = Kilojoule × 0.0002778
Multiply any kilojoule value by 0.0002778 to get kilowatt-hour.
Reverse: Kilojoule = Kilowatt-Hour × 3600
Common kilojoule values — factor: 1 kJ = 0.0002778 kWh
| Kilojoule (kJ) | Kilowatt-Hour (kWh) | Context |
|---|---|---|
| 0.001 kJ | 2.778e-07 kWh | 1 J |
| 0.01 kJ | 2.778e-06 kWh | 10 J |
| 0.1 kJ | 2.778e-05 kWh | 100 J |
| 1 kJ | 0.0002778 kWh | 1 kJ |
| 4.184 kJ | 0.001162 kWh | 1 kcal |
| 10 kJ | 0.002778 kWh | 10 kJ |
| 100 kJ | 0.02778 kWh | 100 kJ |
| 1,000 kJ | 0.2778 kWh | 1 MJ |
| 3,600 kJ | 1 kWh | 1 kWh |
| 1e+04 kJ | 2.778 kWh | 10 MJ |
| 1e+05 kJ | 27.78 kWh | 100 MJ |
| 1e+06 kJ | 277.8 kWh | 1 GJ |
| 1e+08 kJ | 2.778e+04 kWh | 100 GJ |
| 1.000e+10 kJ | 2.778e+06 kWh | 10 TJ |
| 1.000e+12 kJ | 2.778e+08 kWh | 1 PJ |
1 kJ = 0.0002778 kWh. Memorize for instant estimates.
Use 0.0002778 as a quick mental multiplier.
Multiply result by 3600 to recover the original kJ value.
Labels food energy in kJ for metric-market nutritional information.
Calculates reaction heat, enthalpy changes, and process energy in kJ.
Measures athlete metabolic rate and substrate oxidation in kJ.
Teaches heat transfer, steam tables, and engine cycles using kJ.
Prescribes energy intake using kJ in countries using metric labels.
Calculates heat duty for reactors, heat exchangers, and distillation in kJ.
The kilojoule (kJ) equals 1,000 joules and is the practical energy unit for food, chemistry, and heating applications in metric countries. Food energy labels in Australia, Europe, and most of the world use kilojoules.
A dietary calorie (kcal) equals 4.184 kJ. A can of soda contains about 600 kJ. The specific heat of water (4.184 kJ/kg·°C) means heating 1 liter of water by 1°C requires 4.184 kJ.
Interesting fact: An average adult needs about 8,000-10,000 kJ (2,000-2,400 kcal) per day. Running a marathon burns approximately 12,500 kJ.
The kilowatt-hour (kWh) is the commercial unit of electrical energy, equal to the energy consumed by a 1,000-watt appliance in one hour (3,600,000 joules). It became standard with the growth of the electrical grid in the late 19th century.
Electricity bills worldwide are denominated in kWh. A typical household uses 300–1,000 kWh per month. An electric car uses about 15–25 kWh per 100 km. Solar panels generate 250–400 kWh per year per panel.
Interesting fact: The average price of electricity in the US is about $0.12 per kWh. One kWh can run a 100W light bulb for 10 hours, charge a smartphone about 100 times, or power a laptop for 2-3 days.
Converting kilojoule to kilowatt-hour is common across energy, nutrition, engineering, and science. Different sectors use different energy units — joules in physics, kcal in nutrition, kWh in electricity, and BTU in HVAC — making accurate conversion essential for cross-disciplinary work and international comparisons.
Quick reference: 5 kJ = 0.001389 kWh and 10 kJ = 0.002778 kWh. Reverse: 1 kWh = 3600 kJ. Exact factor: 1 kJ = 0.0002778 kWh.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.