Energy Converter

Convert between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTUs, electronvolts, and foot-pounds.

Value

From

Common Energy Conversions

From	To	Result
1 kcal	kJ	4.184 kJ
1 kWh	MJ	3.6 MJ
1 kWh	BTU	3,412.14 BTU
1 BTU	kJ	1.05506 kJ
1 kcal	Wh	1.16222 Wh
1 kJ	kcal	0.239006 kcal
1 J	cal	0.239006 cal
1 ft·lb	J	1.35582 J

Frequently Asked Questions

A small calorie (cal) is the energy needed to raise 1 gram of water by 1°C. A kilocalorie (kcal) = 1000 cal. Food "Calories" (with capital C) are actually kilocalories. So when a food label says "200 Calories," it means 200 kcal = 836.8 kJ.

One kilowatt-hour equals 3,600,000 joules (3.6 MJ). This is because 1 kW = 1000 J/s, and 1 hour = 3600 s. The kWh is the standard unit for electrical energy consumption on utility bills worldwide.

A British Thermal Unit (BTU) is the amount of energy needed to raise 1 pound of water by 1°F. 1 BTU ≈ 1,055.06 joules. It is used in the US for heating and cooling (HVAC), furnaces, air conditioners, and water heaters. The rest of the world uses kJ or kWh.

An electronvolt (eV) is the energy gained by an electron moving through a potential difference of 1 volt. 1 eV = 1.602 × 10⁻¹⁹ joules. It is used in particle physics, atomic physics, and quantum mechanics to describe energies of subatomic particles and photons.

How It Works

Enter Energy

Enter any energy value. All conversions use the joule (J) as the SI base unit of energy.

Pick Units

Choose from 10 energy units spanning everyday food calories to scientific electronvolts and engineering BTUs.

Instant Result

Results are shown instantly. Use the swap button to reverse the conversion and the reference table for quick lookups.

Common Use Cases

Nutrition & Fitness

Convert food energy between kcal and kJ for reading international nutrition labels and comparing dietary energy content.

Electricity Bills

Convert between kWh and joules/MJ to understand energy consumption on utility bills and compare costs of different energy sources.

Heating & Cooling

Convert HVAC ratings between BTU and kW/kJ for comparing heating/cooling equipment specifications across US and international markets.

Renewable Energy

Convert solar panel output, battery capacity, and energy storage between Wh, kWh, and MJ for renewable energy system design.

Physics & Chemistry

Convert between joules, electronvolts, and calories for thermodynamics problems, chemical reaction energies, and quantum physics.

Fuel & Combustion

Convert fuel calorific values between BTU, kJ, and MJ for comparing energy densities of natural gas, coal, oil, and biofuels.

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