Energy Converter: Joules, Calories, kWh, BTU

Last updated: October 2026

From

Formula

1 kJ = 0.2390057 kcal

All Results

J 1,000

kJ 1

MJ 0.001

cal 239.006

kcal 0.239006

kWh 0.000277778

Wh 0.277778

BTU 0.947813

Quick Reference Table: Kilojoule → Kilocalorie

Value (kJ)	Result (kcal)
1 kJ	0.239006 kcal
5 kJ	1.195 kcal
10 kJ	2.3901 kcal
50 kJ	11.9503 kcal
100 kJ	23.9006 kcal
500 kJ	119.5029 kcal
1,000 kJ	239.0057 kcal
3,600 kJ	860.4207 kcal

About Energy Conversions

Energy conversions come up in physics, nutrition, engineering and electricity. The joule (J) is the SI unit of energy. A calorie (cal) is the energy needed to warm 1 gram of water by 1 °C; a kilocalorie (kcal) is 1,000 calories and is the unit used on food labels. One kilowatt-hour (kWh) equals 3.6 million joules and is the unit on electricity bills. The British Thermal Unit (BTU) is used for heating and air conditioning. One BTU equals about 1,055 joules.

Everyday Energy

Food, batteries and appliances on one scale. A food "calorie" on a label is a kilocalorie, or 4,184 joules.

Source	kJ	kcal	kWh
AA battery	9.36	2.237	0.0026
Smartphone battery	54	12.91	0.015
Laptop battery	216	51.63	0.06
An apple	260	62.14	0.07222
Slice of bread	330	78.87	0.09167
Can of cola	590	141	0.1639
Fast-food burger	2,210	528.2	0.6139
Daily adult intake (2,000 kcal)	8,368	2,000	2.324
Electric car battery (60 kWh)	216,000	51,630	60
Lightning bolt	5,000,000	1,195,000	1,389

History of the joule and the calorie

Heat and work were once thought to be different things, measured in different units. Once it was shown that one turns into the other at a fixed rate, the joule could measure both; the calorie survives mainly on food labels and in some older tables.

1850 James Prescott Joule published his measurements of the mechanical equivalent of heat: a given amount of work always produces the same amount of heat.
1948 The General Conference on Weights and Measures declared the joule the unit of quantity of heat, and asked for the results of heat measurements to be given in joules.
1956 An international conference on the properties of steam fixed the International Table calorie at exactly 4.1868 J. This converter uses the slightly smaller thermochemical calorie, 4.184 J.

Sources:

Power Temperature