Understanding energy units
A food Calorie is a kilocalorie: 1 kcal = 4,184 J, while 1 small calorie = 4.184 J. kWh measures energy, not power. This registry uses the international-table BTU convention.
Conversion method
For linear units, multiply the input by its factor to the base unit, then divide by the target factor. The table lists definitions where exact and approximate constants where applicable.
| Unit | 1 unit in base units | Definition |
|---|---|---|
| Joule (J) | 1 | Exact definition; display may be rounded |
| Kilojoule (kJ) | 1,000 | Exact definition; display may be rounded |
| Megajoule (MJ) | 1,000,000 | Exact definition; display may be rounded |
| Calorie (small) (cal) | 4.184 | Exact definition; display may be rounded |
| Kilocalorie (food calorie) (kcal) | 4,184 | Exact definition; display may be rounded |
| Watt-hour (Wh) | 3,600 | Exact definition; display may be rounded |
| Kilowatt-hour (kWh) | 3,600,000 | Exact definition; display may be rounded |
| British thermal unit (BTU) | 1,055.05585262 | Approximate / conventional value |
| Therm (US) (thm) | 105,505,585.262 | Approximate / conventional value |
| Foot-pound (ft·lbf) | 1.3558179483 | Approximate / conventional value |
| Electronvolt (eV) | 1.60217663e-19 | Exact definition; display may be rounded |
Worked example and common conversions
10 kcal = 41.84 kJ. Keep full precision during conversion, then round the final result to the precision of your measurement.
| From | To |
|---|---|
| 10 kcal | 41.84 kJ |
| 10 kJ | 2.3900573614 kcal |
| 10 kWh | 36,000,000 J |
| 10 BTU | 0.0029307107 kWh |
| 10 J | 2.3900573614 cal |
| 10 kWh | 34,121.4163312794 BTU |