Joules to Kilowatt Hours
Convert joules (J) to kilowatt hours (kWh). Both measure work and power, and the conversion comes up in nutrition, electricity, fitness work.
The Formula
``
kilowatt hours = joules × 2.77777777778e-7
joules = kilowatt hours × 3600000
`
One joule is 2.7778e-7 kilowatt hours, and one kilowatt hour is 3,600,000 joules.
Conversion Table
| Joules | Kilowatt Hours |
|---|---|
| 1 J | 2.7778e-7 kWh |
| 2 J | 5.5556e-7 kWh |
| 5 J | 1.3889e-6 kWh |
| 10 J | 2.7778e-6 kWh |
| 25 J | 6.9444e-6 kWh |
| 50 J | 1.3889e-5 kWh |
| 100 J | 2.7778e-5 kWh |
| 500 J | 1.3889e-4 kWh |
| 1,000 J | 2.7778e-4 kWh |
The Other Direction
| Kilowatt Hours | Joules |
|---|---|
| 1 kWh | 3,600,000 J |
| 2 kWh | 7,200,000 J |
| 5 kWh | 18,000,000 J |
| 10 kWh | 36,000,000 J |
| 25 kWh | 90,000,000 J |
| 50 kWh | 180,000,000 J |
| 100 kWh | 360,000,000 J |
| 500 kWh | 1,800,000,000 J |
| 1,000 kWh | 3,600,000,000 J |
What Each Unit Is
Joules (J) — the work done by one newton acting over one metre — the SI derived unit of energy. Named for James Prescott Joule, who established the mechanical equivalent of heat.
Kilowatt Hours (kWh) — 1,000 watt-hours, or 3.6 million joules. The unit electricity has been billed in since metering began.
A Sense of Scale
Lifting an apple one metre takes about 1 J- A heartbeat uses roughly 1 J
- A home uses 8–30 kWh a day
- An EV takes 15–20 kWh per 100 km
Precision
The factor 2.77777777778e-7 is rounded. For engineering work carry more digits than the table above, and round only at the end — rounding at each step compounds.
In Code
`javascript
const jouleToKilowattHour = (value) => value * 2.77777777778e-7;
``
Where This Conversion Comes Up
- Nutrition
- Electricity
- Fitness
- Heating
- Fuel
How Many Decimals Do You Need?
Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 J with the factor truncated at each decimal place:
| Decimals kept | Factor | 137 J becomes | Error |
|---|---|---|---|
| 0 | 0 | 0 | 100.0000% |
| 1 | 0 | 0 | 100.0000% |
| 2 | 0 | 0 | 100.0000% |
| 3 | 0 | 0 | 100.0000% |
| 4 | 0 | 0 | 100.0000% |
The right number of significant figures is set by your input, not by the converter. If you measured joules to three significant figures, the answer in kilowatt hours is only good to three — writing more digits claims precision the measurement never had.