Energy Converter

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

Value
From
To
1 Kilocalorie = — Kilojoules
Common Energy Conversions
FromToResult
1 kcalkJ4.184 kJ
1 kWhMJ3.6 MJ
1 kWhBTU3,412.14 BTU
1 BTUkJ1.05506 kJ
1 kcalWh1.16222 Wh
1 kJkcal0.239006 kcal
1 Jcal0.239006 cal
1 ft·lbJ1.35582 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.
A joule (J) is the SI unit of energy. A small calorie (cal) is the energy to raise 1 gram of water by 1°C, equal to 4.184 joules. A food Calorie (kcal) = 1,000 cal = 4,184 joules. Joules are used in physics and engineering; calories are used in nutrition and chemistry.
A kilowatt-hour (kWh) = 3,600,000 joules = the energy used by a 1,000-watt appliance running for one hour. Electricity bills charge per kWh. A typical US home uses about 900 kWh per month. Running a 100W light bulb for 10 hours = 1 kWh. Average US electricity cost is about $0.13–0.17 per kWh.
A BTU (British Thermal Unit) = 1,055.06 joules = the energy to raise 1 pound of water by 1°F. In HVAC, air conditioner capacity is rated in BTU/hr. A "1-ton" AC unit = 12,000 BTU/hr ≈ 3.52 kW. A typical home might need 24,000–48,000 BTU/hr of cooling depending on climate and house size.
In nutrition, the "Calorie" (capital C) = 1 kilocalorie (kcal) = 1,000 small calories. Food labels list Calories (kcal). A typical adult needs 2,000–2,500 kcal per day. 1 kcal = 4,184 joules. Fat provides 9 kcal/gram, while protein and carbohydrates each provide 4 kcal/gram.
Gasoline contains about 34.2 MJ/liter (8,176 kcal/liter) — roughly 8,000 times more energy per liter than most foods by weight. Burning 1 liter of petrol releases energy equivalent to about 8,000 food Calories. The human body is about 20–25% efficient at converting food energy to mechanical work, similar to a gasoline engine.
A megawatt-hour (MWh) = 1,000 kWh, and a gigawatt-hour (GWh) = 1,000 MWh = 1,000,000 kWh. These units are used for large-scale power generation and consumption. A large coal power plant (1 GW) running for one hour produces 1 GWh. Annual energy consumption of a country is often measured in terawatt-hours (TWh = 1,000 GWh).

About This Energy Converter

This free energy converter converts between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, electron volts, BTUs, and other energy units. Enter a value in any unit for instant results.

When to use this converter

  • Converting food energy between kcal and kJ
  • Comparing electricity consumption figures in kWh
  • Translating physics problems between SI and imperial energy units
  • Converting HVAC ratings between BTU and kW

Standards & References

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