Energy Unit Conversion
Quick answer: 1 kWh = 3.6 MJ = 3,600,000 J ≈ 860 kcal ≈ 3,412 BTU, 1 kcal (IT) = 4.1868 kJ, 1 BTU = 1,055.06 J and 1 toe = 41.868 GJ ≈ 11,630 kWh.
Joule, kWh, MJ, calorie and kilocalorie, BTU, therm, tonne of oil equivalent, eV and ft·lbf – every energy, work and heat conversion.
How the calculation works
Enter an energy and choose the starting unit (for example kWh, MJ or kcal). The table shows the same energy in joules and multiples, watt-hours, calories, BTU, therms, tonnes of oil and coal equivalent, electronvolts and ft·lbf.
Formula and assumptions
The base unit is the joule (1 J = 1 W·s = 1 N·m). 1 Wh = 3,600 J, 1 kWh = 3.6 MJ. The international calorie is 4.1868 J; the thermochemical one 4.184 J. 1 BTU (IT) = 1,055.05585262 J, 1 therm (EC) = 105,506,000 J, 1 toe = 41.868 GJ (10⁷ kcal), 1 eV = 1.602176634 × 10⁻¹⁹ J.
More worked examples
- Annual use of 4,500 kWh: 4,500 × 3.6 = 16,200 MJ = 16.2 GJ.
- A heating value of 10 kWh in kcal: 10 × 859.85 ≈ 8,598 kcal.
- An AC unit at 12,000 BTU (energy for 1 h) ≈ 3.52 kWh.
- Food at 2,000 kcal: 2,000 × 4.1868 = 8,374 kJ ≈ 2.33 kWh.
Units of energy
| Unit | in J | Other |
|---|---|---|
| 1 J | 1 | 1 W·s |
| 1 kJ | 1,000 | 0.239 kcal |
| 1 kcal | 4,186.8 | 1.163 Wh |
| 1 BTU | 1,055.06 | 0.293 Wh |
| 1 kWh | 3,600,000 | 3.6 MJ |
| 1 therm (EC) | 105,506,000 | 29.31 kWh |
| 1 toe | 41,868,000,000 | 11,630 kWh |
Common mistakes
- Mixing kW (power) and kWh (energy).
- Confusing the IT calorie (4.1868 J) with the thermochemical one (4.184 J).
- Treating an air conditioner’s “BTU” as energy – it is really BTU/h (power).
Frequently asked questions
How many MJ are in 1 kWh?
1 kWh = 3.6 MJ. Conversely 1 MJ ≈ 0.2778 kWh.
How many kJ are in 1 kcal?
One (international) kilocalorie is 4.1868 kJ; the food “Calorie” is actually a kilocalorie.
How many kWh is 1 BTU?
1 BTU ≈ 0.000293 kWh, so 1 kWh ≈ 3,412 BTU.
What is a tonne of oil equivalent (toe)?
The energy released by burning a tonne of crude oil, by convention 41.868 GJ = 10⁷ kcal ≈ 11,630 kWh. It is used in energy statistics.
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