CONVERSIONS

Convert between joules, calories, watt-hours, BTU, and more. Enter a value and pick the units.

Value

From

Converted

—

In the target unit.

Usage Tip

Useful anchors: 1 kWh ≈ 3412 BTU, 1 kcal = 4184 J, 1 BTU ≈ 1055 J.

THE MATH

Convert to a base unit, then to the target:
result = value × (from factor ÷ to factor)

Energy converts through joules. Electrical billing uses kWh; food labels use kcal (the food Calorie); heating and cooling often use BTU.
A food Calorie (capital C) is one kilocalorie.

The food Calorie is a kilocalorie — a 100 Calorie snack is 100 kcal = 418,400 J.
1 kWh (a unit of electricity) = 3.6 MJ ≈ 3412 BTU.
BTU is common for heating, cooling, and appliance ratings.

Practical Notes

Energy can be expressed in many units. A joule is the standard SI unit, a watt-hour equals 3,600 joules, a thermochemical calorie equals 4.184 joules, and a BTU is about 1,055 joules. The kilowatt-hour on a power bill is 3.6 million joules.

The calories on food labels are actually kilocalories, so one food Calorie equals 1,000 small calories, or about 4,184 joules. Heating and cooling equipment often uses BTU, electric bills use kilowatt-hours, and physics and engineering use joules. Be careful not to confuse energy with power: a watt is a rate of energy use of one joule per second, while a watt-hour is an amount of energy.

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