Energy converter
E = P × t
Convert an energy between joules, kilojoules, megajoules, thermochemical calories and kilocalories, watt-hours and kilowatt-hours, electronvolts, kilo- and megaelectronvolts, and BTU. Calorie and BTU have several competing definitions: the one used is displayed, not assumed.
1 Thermochemical kilocalorie (kcal) = 4.184 Kilojoule (kJ)
Raw value: 4.184
Scientific dossier
What the tool computes, what it assumes, where it stops being valid, and where its data comes from.
Method & formulasE = P × t
E = P × t
1 Wh = 3600 J (exactly)
1 eV = 1.602176634 × 10⁻¹⁹ J (exactly)
An energy is a power integrated over a duration. The electronvolt has been exact since the 2019 SI redefinition, which fixed the elementary charge: it is no longer a measured value but a definition.
- J
- · Joule (J)
- kJ
- · Kilojoule (kJ)
- MJ
- · Megajoule (MJ)
- cal
- · Thermochemical calorie (cal)
- kcal
- · Thermochemical kilocalorie (kcal)
- Wh
- · Watt-hour (Wh)
- kWh
- · Kilowatt-hour (kWh)
- eV
- · Electronvolt (eV)
- keV
- · Kiloelectronvolt (keV)
- MeV
- · Megaelectronvolt (MeV)
- BTU
- · BTU (international table)
- cal
- · Thermochemical calorie (exactly 4.184 J). The international-table calorie (4.1868 J) and the 15 °C calorie (≈ 4.1855 J) are other definitions in use.
- kcal
- · Thermochemical kilocalorie (exactly 4184 J), the “Calorie” of nutrition labelling.
- BTU
- · International-table BTU (1055.05585262 J). At least five BTU definitions coexist (thermochemical, 39 °F, 59 °F, 60 °F), differing by a few tenths of a percent.
At least three calories coexist: thermochemical (exactly 4.184 J), international-table (4.1868 J) and 15 °C (≈ 4.1855 J). The spread reaches 0.07 %, negligible for nutrition but not for a precise thermal balance. This tool applies the thermochemical calorie and states so explicitly. The same caution applies to the BTU, of which at least five definitions circulate.