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Energy Converter

Convert between energy units: Joule, kJ, calorie, kcal, kWh, Wh, BTU, and electronvolt. Complete converter with all equivalences.

How the Energy Converter Works

This tool instantly converts between the main energy units of measurement, from the Joule of the International System to nutrition's kilocalories, from electricity bill kWh to air conditioning BTUs.

Most Common Conversions

FromToFactor
1 kcalkJ4.184
1 kWhkJ3,600
1 kWhkcal860.4
1 BTUkJ1.055
1 calJ4.184

Energy in Daily Life

In everyday life, the two most common energy units are kcal (nutrition) and kWh (electricity).

Electricity bill: the average household consumption is about 10,500 kWh/year in the US. This equals about 37.8 billion Joules.

Nutrition: food labels report energy in both kJ and kcal. The average daily requirement for an adult is about 2,000 kcal (8,368 kJ), equivalent to about 2.33 kWh.

Air conditioning: AC capacity is often expressed in BTU/h. A unit rated at 9,000 BTU/h (~2.6 kW) is suitable for rooms up to 270 sq ft, one rated at 12,000 BTU/h (~3.5 kW) for rooms up to 375 sq ft.

Frequently Asked Questions

How many calories are in 1 Joule?
1 Joule equals about 0.2390 calories. Conversely, 1 calorie (thermochemical) = 4.184 Joules exactly. Note: the "calories" on food labels are actually kilocalories (kcal). So 1 kcal = 4,184 J = 4.184 kJ.
How do you convert kWh to Joules?
1 kWh = 3,600,000 Joules (3.6 MJ). The kilowatt-hour is the unit used on electricity bills: it corresponds to the energy consumed by a 1,000 W device running for 1 hour.
What is a BTU?
The BTU (British Thermal Unit) is the energy unit of the imperial system. 1 BTU = 1,055.06 Joules. It is used for air conditioner ratings: a 9,000 BTU/h unit has a power of about 2.6 kW, suitable for rooms of 250-300 sq ft.