Energy Converter — Joules, Calories, kWh, BTU, eV, Ft-lb
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Understanding Energy Units and Conversions
Energy is the capacity to do work, and it is measured in many different units depending on the context. The SI unit is the joule (J). In everyday life, kilojoules (kJ) and kilocalories (kcal) are used for food energy, kilowatt-hours (kWh) for electricity, and BTU for heating and cooling.
The calorie has two common meanings: the small calorie (cal) equals 4.184 joules, while the large Calorie (Cal or kcal) equals 4,184 joules and is what you see on food labels. One kilowatt-hour equals 3.6 million joules. A British Thermal Unit (BTU) equals 1,055 joules.
At the atomic scale, the electronvolt (eV) equals about 1.6 x 10^-19 joules. The foot-pound (ft-lb) is used in mechanics, equal to about 1.356 joules. This converter handles all these units with precise conversion factors.
Frequently Asked Questions
What is the difference between a calorie and a kilocalorie?
A small calorie (cal) equals 4.184 joules. A kilocalorie (kcal), also written as Calorie (capital C), equals 1,000 small calories or 4,184 joules. Food labels use kilocalories.
How many joules are in a kilowatt-hour?
One kilowatt-hour (kWh) equals 3,600,000 joules (3.6 MJ). This is 1,000 watts times 3,600 seconds.
What is a BTU and where is it used?
A British Thermal Unit (BTU) equals about 1,055 joules. BTUs are widely used in HVAC to rate furnaces, air conditioners, and water heaters.
How do electronvolts relate to joules?
One electronvolt (eV) equals approximately 1.602 x 10^-19 joules. It is the energy gained by a single electron moving through one volt of electric potential.