A British Thermal Unit (BTU) is the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. 1 BTU = 1,055.06 joules.

Energy Converter

Convert between joules, calories, watt-hours, BTU, electron volts and more

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Key Formulas

1 cal = 4.184 J

1 kWh = 3,600,000 J

1 BTU = 1,055.06 J

1 eV = 1.602 × 10⁻¹⁹ J

How Energy Conversion Works

Energy measures the ability to do work. The joule (J) is the SI unit. Different fields use different units: physics (joules), nutrition (calories), electricity (watt-hours), HVAC (BTU).

Common Energy Units

Joule (J): The SI unit. 1 J = 1 kg·m²/s².
Calorie (cal): Energy to heat 1 gram of water by 1°C. Food calories are kilocalories.
Watt-hour (Wh): Energy consumed by 1 watt for 1 hour. Your electricity bill uses kWh.
BTU: British Thermal Unit. Used for heating/cooling. 1 BTU = 1,055.06 J.

Frequently Asked Questions

What is the difference between a calorie and a kilocalorie?

1 kcal = 1,000 cal. Food "Calories" (capital C) are kilocalories. When a food label says 100 Calories, it means 100 kcal.

How many joules are in a calorie?

1 cal = 4.184 joules. 1 kcal (food calorie) = 4,184 joules.

What is a BTU?

A BTU is the heat to raise 1 pound of water by 1°F. 1 BTU = 1,055.06 joules. Used in HVAC systems.

How do you convert watt-hours to joules?

Multiply watt-hours by 3,600 to get joules. 1 Wh = 3,600 J.

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