Energy Converter — joules to calories, calories to joules, BTU to kWh, kWh to joules
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Energy Conversions — joules to calories, calories to joules, BTU to kWh, kWh to joules

Quick energy conversions commonly used for physics, nutrition, engineering and everyday calculations. Convert joules to calories, calories to joules, kcal to joules, BTU to kWh, kWh to joules, electronvolts to joules and more.

Unit descriptions

Joules (J)

The SI unit of energy. 1 joule = 1 newton-meter = 1 watt-second. Used in physics and engineering worldwide.

Calories (cal)

Common unit for food energy. 1 calorie = 4.184 joules. Note: nutritional "Calories" (with capital C) are actually kilocalories.

Kilocalories (kcal)

The "Calorie" used on food labels. 1 kcal = 1,000 calories = 4,184 joules. Represents the energy needed to raise 1kg of water by 1°C.

British Thermal Units (BTU)

Common in heating and cooling systems. 1 BTU ≈ 1,055 joules. Represents the energy needed to raise 1 pound of water by 1°F.

Kilowatt-hours (kWh)

Standard unit for electricity billing. 1 kWh = 3.6 million joules. Represents 1,000 watts used for 1 hour.

Browse Energy Conversions

Joules Calories Kilocalories BTU kWh Electronvolts Watt-hours

Energy Conversion Tables

1 joule (J)
= 0.2390057361 cal · = 0.0009478171 BTU · = 2.77778e-7 kWh
1 calorie (cal)
= 4.184 J · = 0.0039656668 BTU · = 1.16222e-6 kWh
1 kilocalorie (kcal)
= 4,184 J · = 3.9656668 BTU · = 0.00116222 kWh
1 BTU
= 1,055.05585262 J · = 252.16440072 cal · = 0.0002930711 kWh
1 kWh
= 3,600,000 J · = 859,845.227859 cal · = 3,412.1416331 BTU
1 electronvolt (eV)
= 1.602176634e-19 J · = 3.826734e-20 cal
1 watt-hour (Wh)
= 3,600 J · = 860.4206501 cal · = 3.4121416331 BTU

Common Energy Conversions

Daily calorie intake (2000 kcal)
= 8,368,000 J · = 7,931.3336 BTU · = 2.32444 kWh
Apple (95 kcal)
= 397,480 J · = 376.73 BTU · = 0.11041 kWh
1 hour of laptop use
≈ 50 Wh = 180,000 J = 43.02 kcal
Household monthly electricity (300 kWh)
= 1.08e9 J · = 1,023,642.5 BTU · = 257,953.5 kcal
Car battery (60 kWh)
= 216,000,000 J · = 204,728,498 BTU · = 51,590,700 cal
TNT explosion (1 ton)
= 4.184e9 J · = 1.0e9 cal · = 1,162.22 kWh

Energy in Different Contexts

Food Energy
Measured in kilocalories (kcal), often called "Calories"
Electrical Energy
Measured in kilowatt-hours (kWh) for billing
Heat Energy
Often measured in BTU for HVAC systems
Physics/Chemistry
Joules standard, electronvolts for atomic scale

Important: Nutritional "Calories" (capital C) are actually kilocalories (kcal). When converting food energy, 1 Calorie = 1 kcal = 4,184 joules. For small calories (thermochemical), 1 cal = 4.184 J.

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