Energy Converter
Convert between joules, kilojoules, calories, kilocalories (food Calories), watt-hours, kilowatt-hours and BTU — instantly and accurately.
Energy Converter
Energy — Result
0.001 kJ
1 Joule = 0.001 Kilojoule
How It Works
Energy comes in many units because it appears in so many fields — physics, nutrition, electricity and heating. The SI unit is the joule (J). Food labels use kilocalories (kcal, the “Calories” with a capital C), electricity bills use kilowatt-hours (kWh), and heating and air-conditioning often use BTU (British thermal units). This converter translates everything through the joule: your value is multiplied by its factor to get joules, then divided by the target unit’s factor. Some handy equivalences: one kilocalorie is 4,184 joules, one watt-hour is 3,600 joules (so one kilowatt-hour is 3.6 million joules), and one BTU is about 1,055 joules. That means the ~2,000 kcal in a daily diet is roughly 8.4 million joules, or about 2.3 kWh of energy. Choose your units, enter a value, and see the conversion at once.
Formula
Convert via the SI base unit Joule (J): value in J = input × factor; result = J ÷ target factor. 1 kcal = 4,184 J; 1 kWh = 3,600,000 J; 1 BTU ≈ 1,055.06 J.
Frequently Asked Questions
How many joules are in a calorie?
One (small) calorie is 4.184 joules, and one kilocalorie (food Calorie) is 4,184 joules. Nutrition labels use kilocalories, often written simply as “Calories”.
How many joules are in a kWh?
3,600,000 joules. A kilowatt-hour is 1,000 watts sustained for one hour, and since one watt is one joule per second, that is 1,000 × 3,600 = 3.6 million joules.
What is a BTU?
A British thermal unit is the energy to raise one pound of water by 1°F — about 1,055 joules. BTUs are common in heating, cooling and air-conditioner ratings.
Is a food Calorie the same as a calorie?
A food “Calorie” (capital C) is actually a kilocalorie — 1,000 small calories, or 4,184 joules. So a 100-Calorie snack contains about 418,400 joules of energy.
How much energy is a daily diet?
A typical 2,000 kcal daily diet is about 8.37 million joules (8.37 MJ), or roughly 2.3 kilowatt-hours — enough to power a 100 W bulb for nearly a day.