Energy Converter
Use this energy converter to convert between joules, kilojoules, kilowatt-hours, kilocalories, BTU and other units. One kilowatt-hour is 3.6 megajoules, 3,600 kilojoules, 860.42 kilocalories or 3,412.14 BTU. An appliance drawing 100 watts runs for 10 hours on it.
Example: Energy 1 · Convert from: Kilowatt-hours (kWh) · Convert to: British thermal units (BTU) · Appliance power (optional) 100 W → Result: 1 kWh = 3,412.142 BTU. Source: NIST SP 811 – Guide for the Use of the International System of Units, appendix B: energy conversion factors (calorie, BTU, foot-pound force). Updated: .
How it is calculated
How to convert energy units
All units are defined through the joule. The converter first turns the value into joules and then into the target unit: result = value × joules of the source unit ÷ joules of the target unit. For 1 kWh in MJ that is 1 × 3,600,000 ÷ 1,000,000 = 3.6.
The key factors
- 1 Wh = 3,600 J, 1 kWh = 3.6 MJ.
- 1 cal (thermochemical calorie) = 4.184 J, 1 kcal = 4.184 kJ. The food calorie on packaging is the kilocalorie.
- 1 BTU (International Table) = 1,055.056 J, 1 ft·lbf = 1.3558 J, 1 eV = 1.602 × 10⁻¹⁹ J.
Appliance run time
Energy divided by power gives time: 1 kWh ÷ 100 W = 10 hours. Enter the power of an appliance and the converter shows how long the energy lasts.
Limits
There are several definitions of the calorie: the converter uses the thermochemical one (4.184 J); the International Table calorie is 4.1868 J. The converter does not account for fuel heating values, efficiencies or tariffs; it only converts units into each other.
Frequently asked questions
How many kcal are in a kWh?
One kilowatt-hour is 860.42 kilocalories, because 3,600,000 J divided by 4,184 J gives 860.42.
How many kJ are 100 kcal?
100 kcal are 418.4 kJ, because 1 kcal is exactly 4.184 kJ.
How do you convert joules to kWh?
Divide by 3,600,000. 7.2 million joules are 2 kWh.
What is a BTU?
A British thermal unit is about 1,055 joules. 1 kWh equals roughly 3,412 BTU.
What is the difference between a calorie and a kilocalorie?
A kilocalorie is 1,000 calories. The “calories” on food labels are kilocalories.
Sources and legal basis
- NIST SP 811 – Guide for the Use of the International System of Units, appendix B: energy conversion factors (calorie, BTU, foot-pound force)
- Wikipedia – Joule: definition and conversion to watt-hour, calorie and electronvolt
- Wikipedia – British thermal unit: 1 BTU (IT) = 1055.056 J
As of: · Editorial policy
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