Energy Converter
Quick answer: Choose a starting unit and a target unit, then enter a value. Common conversions: 1 kcal = 4.184 kJ; 1 J = 0.001 kJ; 1 J = 0.0002390057 kcal. This converter covers 12 energy units.
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Use the Energy Converter
Energy formula and what each symbol means
target = value × (factor of starting unit ÷ factor of target unit), where each factor is the unit value in J.
| Symbol | Meaning |
|---|---|
| value | The number you want to convert |
| factor | The unit’s size expressed in the base unit (J) |
Energy examples
kcal to kJ
10 kcal = 41.84 kJ.
J to kJ
10 J = 0.01 kJ.
J to kcal
10 J = 0.002390057 kcal.
How to calculate Energy step by step
- Choose the starting unit and the target unit.
- Enter your value.
- Read the converted value, plus the conversion factor in both directions.
Popular energy conversions
- Joules to kJ converter
- Joules to Kilocalories converter
- Joules to kWh converter
- Joules to BTU converter
- Joules to Calories converter
- kJ to Joules converter
- kJ to Kilocalories converter
- kJ to kWh converter
- kJ to BTU converter
- kJ to Calories converter
- Kilocalories to Joules converter
- Kilocalories to kJ converter
- Kilocalories to kWh converter
- Kilocalories to BTU converter
- Kilocalories to Calories converter
- kWh to Joules converter
How to read your Energy result
The joule is the SI unit of energy. Food labels use the kilocalorie (kcal, written Calorie in the US), electricity bills use the kilowatt hour, and heating uses the Btu. One kilocalorie is exactly 4,184 J and one kilowatt hour is exactly 3.6 million joules.
| UNIT | SYMBOL | EQUALS | VALUE OF 1 J |
|---|---|---|---|
| Joule | J | 1 J = 1 J | 1 J |
| Kilojoule | kJ | 1 kJ = 1,000 J | 0.001 kJ |
| Megajoule | MJ | 1 MJ = 1,000,000 J | 0.000001 MJ |
| Watt hour | Wh | 1 Wh = 3,600 J | 0.0002777778 Wh |
| Kilowatt hour | kWh | 1 kWh = 3,600,000 J | 2.777778×10⁻⁷ kWh |
| Calorie (thermochemical) | cal | 1 cal = 4.184 J | 0.2390057 cal |
| Kilocalorie (food Calorie) | kcal | 1 kcal = 4,184 J | 0.0002390057 kcal |
| British thermal unit (ISO) | Btu | 1 Btu = 1,055.0559 J | 0.0009478171 Btu |
| Electron volt | eV | 1 eV = 1.6021766×10⁻¹⁹ J | 6.241509×10¹⁸ eV |
| Foot pound-force | ft·lbf | 1 ft·lbf = 1.3558179 J | 0.7375621 ft·lbf |
| Therm (US) | thm | 1 thm = 105,480,400 J | 9.480434×10⁻⁹ thm |
| Erg | erg | 1 erg = 1×10⁻⁷ J | 10,000,000 erg |
Common mistakes when calculating Energy
- Mixing the small calorie (cal) with the food Calorie (kcal): the difference is a factor of 1,000.
- Confusing kW (power) with kWh (energy).
- Using different Btu definitions: this tool uses the International Table Btu of 1,055.05585262 J.
Energy FAQ
How many joules are in a kilocalorie?
One thermochemical kilocalorie is exactly 4,184 joules.
How many kJ are in a kWh?
One kilowatt hour is exactly 3,600 kJ.
How many Btu are in a kWh?
One kWh is about 3,412.14 Btu (International Table).
What is the base unit for energy?
This converter uses joule (J) as the common base unit: every value is first converted to it and then to the target unit.
How do I convert between two energy units?
Choose the starting and target units, enter the value and read the result. By hand: convert to the base unit with the table, then divide by the target unit factor.
How many kJ are in 1 kilocalorie?
1 kcal = 4.184 kJ.
How many kJ are in 1 joule?
1 J = 0.001 kJ.
How many kilocalories are in 1 joule?
1 J = 0.0002390057 kcal.
Which energy units does this converter support?
It covers 12 units: joule (J), kilojoule (kJ), megajoule (MJ), watt hour (Wh), kilowatt hour (kWh), calorie (cal), kilocalorie (kcal), british thermal unit (Btu), electron volt (eV), foot pound-force (ft·lbf), therm (thm), erg (erg).
How accurate is the energy converter?
Results are calculated at full double precision and shown to about 8 significant figures. Round the answer to the precision of your original measurement; a result cannot be more accurate than the number you started with.
More in Energy converters
- Joules to BTU Converter
- Calories to kWh Converter
- Joules to Calories Converter
- Calories to kJ Converter
- Calories to Kilocalories Converter
- Calories to Joules Converter
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Method, review and disclaimer
Edited by: Hemant Kumar and Anjita Rai, founders of ToolsVault (SEO and content professional, not a licensed adviser). Method: this tool runs in your browser using the formula shown on this page; the numbers you enter are not sent to our servers. Sources: NIST SP 811, Appendix B.8: conversion factors