Energy Unit Converter

Conversion Result

Converted to All Units

Common Energy Conversions

Joules & Calories

• • 1 joule = 0.239006 calories (thermochemical)
• • 1 calorie (thermo.) = 4.184 joules
• • 1 kilocalorie (food Cal) = 4,184 joules
• • 1 kilojoule = 0.239006 kilocalories

  Electrical & Thermal

  • • 1 kWh = 3,600,000 joules
  • • 1 kWh = 3,412.14 BTU
  • • 1 BTU = 1,055.06 joules
  • • 1 therm = 100,000 BTU

    Understanding Energy Units

    Energy is the capacity to do work or produce heat. It is one of the most fundamental concepts in physics and is conserved in all processes (First Law of Thermodynamics). Because energy appears in so many contexts — mechanics, electricity, chemistry, nutrition, and nuclear physics — a wide variety of units have evolved, each suited to its own domain. The SI unit of energy is the joule (J), defined as the work done when a force of one newton displaces an object by one meter.

    SI / Metric Units

    • Joule (J): The SI derived unit of energy, equal to 1 kg·m²/s². Named after James Prescott Joule, who demonstrated the relationship between mechanical work and heat.
    • Kilojoule (kJ): 1,000 joules. Commonly used in nutrition labelling outside the United States and in chemistry.
    • Megajoule (MJ): 1,000,000 joules. Used for industrial energy consumption, fuel energy content, and engineering.
    • Gigajoule (GJ): 1,000,000,000 joules. Used in energy economics and large-scale industrial processes.
    • Watt-hour (Wh) / Kilowatt-hour (kWh): 1 Wh = 3,600 joules. The kilowatt-hour is the standard unit for measuring electrical energy consumption on utility bills. 1 kWh = 3.6 MJ.
    • Megawatt-hour (MWh): 1,000 kWh. Used for utility-scale electricity generation and large commercial energy usage.

      Calorie Units

      • Thermochemical calorie (cal): Defined as exactly 4.184 joules. Used in physical chemistry and thermodynamics.
      • International Table calorie (cal_{IT): Defined as exactly 4.1868 joules. Adopted by the International Steam Table Conference and used in steam engineering.}
      • Kilocalorie / food Calorie (kcal): 1,000 thermochemical calories (4,184 joules). The "Calorie" with a capital C seen on food labels in the United States is actually a kilocalorie.

        Imperial / US Units

        • British Thermal Unit (BTU): The amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. Approximately 1,055.06 joules. Widely used in HVAC, heating, and the US energy industry.
        • Therm (thm): Defined as exactly 100,000 BTU (approximately 105.506 MJ). Used by natural gas utilities in the United States and United Kingdom for billing.
        • Foot-pound force (ft·lbf): The work done when a force of one pound-force displaces an object by one foot. Approximately 1.35582 joules. Used in mechanical engineering and torque specifications.

          Scientific Units

          • Electronvolt (eV): The energy gained by an electron moving through an electric potential difference of one volt. Exactly 1.602176634 × 10^{−19 joules. The fundamental unit of energy in atomic, nuclear, and particle physics.}
          • Kiloelectronvolt (keV) / Megaelectronvolt (MeV): 1,000 eV and 1,000,000 eV respectively. Used in X-ray spectroscopy, nuclear physics, and radiation therapy.
          • Erg: The CGS unit of energy, equal to exactly 10−7 joules (0.1 µJ). Still found in some astrophysics literature and older scientific publications.

            Large-Scale & Industrial Units

            Ton of TNT (tTNT)

            A conventional measure of explosive energy equal to exactly 4.184 × 10^{9 joules (4.184 GJ). Used to express the energy release of explosions and asteroid impacts. The atomic bomb dropped on Hiroshima released approximately 15 kilotons of TNT equivalent.}

            Tonne of Oil Equivalent (toe)

            Defined by the International Energy Agency as exactly 41.868 GJ (approximately 11,630 kWh). Represents the approximate amount of energy released by burning one metric tonne of crude oil. Used in global energy statistics and policy to compare energy sources.

            Energy in Everyday Context

            Nutrition

            • • Apple: ~95 kcal (398 kJ)
            • • Banana: ~105 kcal (439 kJ)
            • • Daily adult intake: ~2,000 kcal
            • • 2,000 kcal = 8,368 kJ = 2.326 kWh

              Household Energy

              • • LED bulb (10 W, 1 hr): 36 kJ
              • • Microwave (1 kW, 5 min): 300 kJ
              • • EV full charge: ~60 kWh
              • • US home monthly avg: ~900 kWh

                Fuels

                • • 1 gallon gasoline: ~132 MJ
                • • 1 kg hydrogen: ~142 MJ
                • • 1 kg coal: ~24 MJ
                • • 1 barrel crude oil: ~6.1 GJ

                  References

                  The conversion factors used in this calculator are based on internationally recognized standards and definitions:

                  • BIPM - SI Derived Units (Bureau International des Poids et Mesures)
                  • NIST Guide to SI - Conversion Factors for Energy
                  • NIST CODATA - Electronvolt-Joule Relationship
                  • International Energy Agency (IEA) - Unit Converter
                  • U.S. Energy Information Administration - Units and Calculators

                    Note: All conversions use exact or internationally accepted values. The joule is the SI derived unit of energy defined as 1 kg·m²/s². The thermochemical calorie is defined as exactly 4.184 J, and the electronvolt as exactly 1.602176634 × 10^{−19 J (2019 SI redefinition). The BTU value used here is the International Table BTU (1 BTU_{IT = 1,055.05585262 J).}}

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