Energy Converter

Convert between joule, kilowatt-hour, calorie, BTU, watt-hour, electron-volt, and many other energy and power units with scientific precision.

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Energy Units Explained

Joule (J)

The SI unit of energy, equal to one watt of power for one second. 1 J = 1 N·m. Fundamental unit for all energy calculations.

Common uses: Scientific calculations, physics, engineering, thermodynamics, mechanical work.

Kilowatt-hour (kWh)

Common energy unit for electricity billing. 1 kWh = 3.6 MJ = 3.6 × 10⁶ J. Energy consumed by 1 kW device in 1 hour.

Common uses: Electricity bills, power consumption, household energy, industrial power usage.

Watt-hour (Wh)

One thousandth of a kilowatt-hour. 1 Wh = 3600 J. Used for battery capacity and power consumption.

Common uses: Battery capacity ratings, portable device energy, electric vehicle batteries.

Calorie (cal) & Kilocalorie (kcal)

Heat energy unit. 1 kcal = 4184 J = 1.163 Wh. Food "calories" are actually kilocalories.

Common uses: Food nutrition labels, dietary energy, thermal energy, heat capacity.

BTU (British Thermal Unit)

Imperial unit of heat energy. 1 BTU ≈ 1055 J. Common in HVAC and heating systems.

Common uses: Air conditioning ratings, heating capacity, HVAC systems, furnace efficiency.

Electron-volt (eV)

Atomic scale energy unit. 1 eV = 1.602 × 10⁻¹⁹ J. Energy of one electron accelerated by one volt.

Common uses: Atomic physics, quantum mechanics, semiconductor properties, radiation energy.

Megajoule (MJ)

One million joules. 1 MJ = 0.277 kWh. Used for larger energy quantities.

Common uses: Industrial energy, fuel energy content, large-scale thermodynamics.

Horsepower-hour (hp·h)

Power unit times time. 1 hp·h ≈ 2.685 MJ. Used in mechanical and industrial contexts.

Common uses: Industrial machinery energy, motor operation, mechanical work calculations.

Therm

Natural gas energy unit. 1 therm ≈ 105.5 MJ. Used in gas utility billing.

Common uses: Natural gas utility bills, heating fuel energy, gas appliance energy ratings.

Newton-meter (N·m)

Unit of torque and work. 1 N·m = 1 J. Represents mechanical work or rotational effort.

Common uses: Mechanical torque, rotational work, mechanical engineering, torque specifications.

Energy Conversions Quick Reference

1 Kilowatt-hour: 3.6 MJ = 3.412 BTU × 10³ = 860 kcal
1 Megajoule: 0.278 kWh = 277.8 Wh = 239 kcal
1 Calorie (nutritional): 4184 J = 4.184 kJ = 1.163 Wh
1 BTU: 1055 J = 1.055 kJ = 0.293 Wh
1 Electron-volt: 1.602 × 10⁻¹⁹ J (atomic scale)
1 Horsepower-hour: 2.685 MJ = 0.746 kWh
Average home daily use: 20-30 kWh = 72-108 MJ
Industrial electricity cost: Typically $0.07-0.12 per kWh

Real-World Energy Equivalents

1 kWh electricity: Lights 100W bulb for 10 hours
1 liter gasoline: ~34.2 MJ = ~9.5 kWh
1 therm natural gas: ~105.5 MJ = ~29.3 kWh
1 food calorie: 4.184 kJ (needed to raise 1 kg water by 1°C)
Running 100W device for 1 hour: 0.1 kWh = 360 kJ
Daily human food intake: ~2000 kcal = ~8.4 MJ
1 ton of TNT: ~4.184 GJ = ~1162 kWh
Lightning strike: ~1-5 GJ (varies greatly)