Convert Joule to Kilowatt-Hour (J → kWh)

Converting joules to kilowatt-hours is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in joules

   Start with the number of joules (J) you want to convert.
2. 2
   Multiply by 2.778e-7

   The conversion factor from J to kWh is 2.778e-7. Multiply your value by this number.
3. 3
   Read the result in kilowatt-hours

   The result is your value in kilowatt-hours (kWh).

Multiply the value in joules by 2.778e-7. For the reverse direction, multiply by 3,600,000.

• ✓1 J = 1 N·m = 1 W·s.
• ✓1 kWh = 3,600,000 J (3.6 MJ).
• ✓For nutrition 1 kcal = 4.184 kJ.

• ✗Confusing joule (energy) with newton (force).
• ✗Mixing joule with watt — watt is joule per second.
• ✗Using kJ when labels call for kcal on US nutrition.

What is the Joule?

The joule is the SI unit of energy, work, and heat, named after English physicist James Prescott Joule (1818–1889). Defined as the energy transferred when a force of one newton acts over a distance of one meter (1 J = 1 N·m), the joule unifies mechanical work, electrical energy (1 J = 1 watt-second = 1 V·C), and thermal energy. A typical apple has about 250,000 joules of chemical energy when metabolized, lifting an apple 1 meter requires roughly 1 joule of mechanical work, and a single joule could light a 1-watt LED for one second. The joule is fundamental in physics, mechanical engineering, electrical engineering, and nutrition (European food labels show kilojoules). It relates to the kilojoule (1 kJ = 1,000 J), the calorie (1 cal = 4.184 J), the watt-hour (1 Wh = 3,600 J), and the BTU (1 BTU ≈ 1,055 J). Modern definitions of the kilogram and the Kelvin both reference the joule.

• Physics and engineering calculations
• Scientific nutrition measurement (European labels)
• Impact energy in engineering (Charpy test)

What is the Kilowatt-Hour?

The kilowatt-hour equals 1,000 watt-hours (3.6 megajoules) and is the universal billing unit for residential electricity consumption around the world. A typical US household uses about 800–1,000 kWh per month; a refrigerator consumes 1–2 kWh per day, an LED bulb at 10 W for 10 hours uses 0.1 kWh, and a Tesla Model 3 has a 75 kWh battery (about 250–350 miles of range). Electric utility rates are quoted in cents per kWh — typical US residential rates are 11–25 ¢/kWh, while industrial rates are lower. The kilowatt-hour is essential in renewable-energy planning: solar panel output, wind farm production, and grid-scale storage are all rated in kWh or MWh (megawatt-hours). It relates to the watt-hour (1,000 Wh = 1 kWh), the joule (1 kWh = 3.6 MJ), the BTU (1 kWh ≈ 3,412 BTU), and the megawatt-hour (1,000 kWh = 1 MWh).

• Electricity billing globally
• EV battery capacity specifications
• Home solar and battery storage