90 free converters, pick a pair below. Instant results, formulas and conversion tables included.
Energy spans physics, nutrition and engineering, and the units do not always advertise which field they belong to. The calorie on a food label is really a kilocalorie, 4,184 joules, a thousand times the small calorie used in a laboratory. Capitalizing Calorie is the traditional way of signalling the large one, and it is why a 2,000 Calorie diet is 2,000,000 small calories.
At home, electricity is billed in kilowatt-hours of 3,600,000 J each, and heating and cooling equipment is rated in BTU, which is 1,055.06 J. In physics the electronvolt is the natural unit at atomic scale, 1.602176634 x 10^-19 J, and it is the reason particle masses are quoted in GeV.
| J | kJ | cal | kcal | kWh | BTU | ft·lb | eV | |
|---|---|---|---|---|---|---|---|---|
| 1 J | 1 | 0.001 | 0.239006 | 0.000239 | 2.7778e-07 | 0.000948 | 0.737562 | 6.2415e+18 |
| 1 kJ | 1000 | 1 | 239.005736 | 0.239006 | 0.000278 | 0.947817 | 737.562149 | 6.2415e+21 |
| 1 cal | 4.184 | 0.004184 | 1 | 0.001 | 1.1622e-06 | 0.003966 | 3.08596 | 2.6114e+19 |
| 1 kcal | 4184 | 4.184 | 1000 | 1 | 0.001162 | 3.965667 | 3085.960033 | 2.6114e+22 |
| 1 kWh | 3.6000e+06 | 3600 | 860420.650096 | 860.42065 | 1 | 3412.141633 | 2.6552e+06 | 2.2469e+25 |
| 1 BTU | 1055.055853 | 1.055056 | 252.164401 | 0.252164 | 0.000293 | 1 | 778.169262 | 6.5851e+21 |
| 1 ft·lb | 1.355818 | 0.001356 | 0.324048 | 0.000324 | 3.7662e-07 | 0.001285 | 1 | 8.4624e+18 |
| 1 eV | 1.6022e-19 | 1.6022e-22 | 3.8293e-20 | 3.8293e-23 | 4.4505e-26 | 1.5186e-22 | 1.1817e-19 | 1 |
How many joules are in a calorie? 4.184 for the thermochemical calorie, the value used in nutrition and on this site. A kilocalorie, which is what a food label means by Calorie, is therefore 4,184 J.
How many joules are in a kilowatt-hour? 3,600,000, because a kilowatt-hour is 1,000 watts sustained for 3,600 seconds. That is why a 2 kW appliance running for an hour uses 2 kWh, or 7.2 million joules.
What is a BTU? A British thermal unit, 1,055.05585262 J, historically the energy needed to raise one pound of water by one degree Fahrenheit. Air conditioners and furnaces are sized in BTU per hour.
What is an electronvolt? The energy one electron gains crossing a potential of one volt, 1.602176634 x 10^-19 J. It is tiny in everyday terms, which is exactly what makes it useful for atoms and particles.