Is a food Calorie the same as a calorie?

No — and it causes endless confusion. A food "Calorie" (capital C) is actually a kilocalorie: 1,000 small calories. So a 200-Calorie snack is 200 kcal = 836,800 joules.

How many joules in a kilowatt-hour?

One kWh = 3,600,000 joules (3.6 megajoules). It is the energy of using 1,000 watts for one hour — the unit your electricity bill charges by.

What is an electronvolt?

The energy an electron gains crossing a 1-volt potential — about 1.602 × 10⁻¹⁹ joules. It is tiny, which is why it suits particle and atomic physics.

Energy Converter

Convert energy units — joules, calories, kilowatt-hours, BTU, and electronvolts. For physics, nutrition, and utility bills.

Converters

Joule J

Kilojoule kJ

Calorie cal

Kilocalorie (food Cal) kcal

Watt-hour Wh

Kilowatt-hour kWh

British thermal unit BTU

Foot-pound ft·lb

Electronvolt eV

About the energy converter

Energy spans an enormous range of units because every field measures it differently: joules in physics, (kilo)calories in nutrition, kilowatt-hours on your electric bill, BTU in heating and cooling, and electronvolts in particle physics. They all measure the same thing — the capacity to do work.

Conversion reference

1 J	=	1 J	Joule
1 J	=	0.001 kJ	Kilojoule
1 J	=	0.23900574 cal	Calorie
1 J	=	0.00023900574 kcal	Kilocalorie (food Cal)
1 J	=	0.00027777778 Wh	Watt-hour
1 J	=	2.7778e-7 kWh	Kilowatt-hour
1 J	=	0.00094781712 BTU	British thermal unit
1 J	=	0.73756215 ft·lb	Foot-pound
1 J	=	6.2415e+18 eV	Electronvolt

All conversions run entirely in your browser — nothing is sent to a server. Factors are exact wherever an exact definition exists.