Energy Converter
Convert between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, and electronvolts.
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All conversions
What is Energy Converter?
An energy converter lets you switch between different units of energy and heat used across physics, nutrition, engineering, and electricity. The SI unit is the joule, but calories are used in food science, kilowatt-hours in electricity billing, BTU in HVAC systems, and electronvolts in particle physics. Conversions are frequently needed when comparing data across these fields.
How to use
- 1 Enter the energy value you want to convert in the Value field.
- 2 Select the source unit from the From dropdown.
- 3 Select the target unit from the To dropdown.
- 4 The result and a full conversion table appear immediately.
- 5 Use the swap button to flip the conversion direction.
Formula
Example calculation
A 2000 kcal diet contains 2000 × 4184 = 8,368,000 joules or 8368 kJ. Expressed in kilowatt-hours: 8,368,000 J / 3,600,000 J/kWh = approximately 2.32 kWh.
Frequently asked questions
What is the difference between a calorie and a kilocalorie?
A small calorie (cal) is the energy needed to raise 1 gram of water by 1 degree Celsius. A kilocalorie (kcal) equals 1000 calories. Nutrition labels and food energy use kilocalories, often labelled just as Calories (with a capital C).
How many joules are in a kilowatt-hour?
One kilowatt-hour equals 3,600,000 joules (3.6 MJ). It represents the energy consumed by a 1000-watt appliance running for one hour and is the standard unit on electricity bills.
What is a BTU?
A British Thermal Unit (BTU) is the amount of heat required to raise one pound of water by one degree Fahrenheit. It equals approximately 1055 joules and is widely used in HVAC, heating systems, and air conditioners in the US.
What is an electronvolt used for?
An electronvolt (eV) is the kinetic energy gained by one electron accelerating through one volt. It equals about 1.602 × 10^-19 joules and is the standard energy unit in atomic physics, chemistry, and particle physics.
How do I convert food Calories to kilojoules?
Multiply Calories (kcal) by 4.184 to get kilojoules. For example, a 250 kcal snack equals 250 × 4.184 = 1046 kJ. Australian and European nutrition labels often show both values.