⚡ Energy Converter
Convert joules, kilocalories, kilowatt-hours, BTUs, electronvolts, and more.
Enter a value above to see the result
Common Energy Conversions
| Input | Unit | Result | Unit |
|---|---|---|---|
| 1 | Kilocalorie | 4.184 | Kilojoule |
| 1 | Kilowatt-hour | 3600 | Kilojoule |
| 1 | BTU | 1055.0559 | Joule |
| 100 | Kilojoule | 23.900574 | Kilocalorie |
| 2000 | Kilocalorie | 2.3244444 | Kilowatt-hour |
| 1 | Kilowatt-hour | 3412.1416 | BTU |
Formula Reference
Key relationships: 1 kWh = 3,600,000 J = 3,600 kJ ≈ 3,412 BTU 1 kcal = 4,184 J = 4.184 kJ (food Calories use kcal) 1 BTU ≈ 1,055 J • 1 cal = 4.184 J
About Energy Conversions
Energy is the capacity to do work or produce heat. It appears in an enormous variety of everyday contexts: the food Calories you track in a diet app, the kilowatt-hours on your electricity bill, the BTU rating on a furnace or air conditioner, and the joules in a physics equation. Because these contexts are so different, a wide range of energy units has developed over time.
The joule (J) is the SI unit of energy. Larger everyday quantities are expressed in kilojoules (kJ) or megajoules (MJ). For electricity consumption, kilowatt-hours (kWh) are practical: 1 kWh is the energy consumed by a 1,000-watt appliance running for exactly one hour, which equals 3,600,000 joules. Your electricity provider charges you per kWh.
In nutrition, energy in food is measured in kilocalories (kcal). These are labeled 'Calories' (with a capital C) on food packaging — so a '200 Calorie' snack contains 200 kcal, or 836,800 joules. The BTU (British Thermal Unit) is used in the United States for heating and cooling equipment ratings. Electronvolts (eV) are used in atomic and particle physics where joules would produce unwieldy tiny numbers.
Frequently Asked Questions
What is the difference between a calorie and a kilocalorie?
A small calorie (cal) is the energy needed to raise 1 gram of water by 1°C. A kilocalorie (kcal) is 1,000 small calories. Food 'Calories' — always capitalized — are actually kilocalories. A '200 Calorie' food item contains 200 kcal, or 836,800 joules. This distinction trips up many people because food packaging uses the capital-C 'Calorie' as shorthand for kilocalorie.
How many joules are in a kilowatt-hour?
One kilowatt-hour (kWh) equals exactly 3,600,000 joules (3.6 MJ). The math: 1 kilowatt = 1,000 watts = 1,000 joules per second. Over one hour (3,600 seconds): 1,000 J/s × 3,600 s = 3,600,000 J. This conversion is useful when comparing your electricity consumption to other energy forms.
What is a BTU used for?
BTU stands for British Thermal Unit — the energy needed to raise one pound of water by 1°F. It equals approximately 1,055 joules. In the US, air conditioners, furnaces, and water heaters are rated in BTUs or BTU/hour. A higher BTU rating means more heating or cooling power.
What is the difference between energy and power?
Energy is the total capacity to do work, measured in joules or kWh. Power is the rate at which energy is used or produced, measured in watts (joules per second). A 100-watt light bulb uses 100 joules every second. Run it for 10 hours and it consumes 1 kWh of energy. Thinking clearly about this distinction helps when reading appliance labels and electricity bills.
How many kilocalories does a person burn per day?
A typical adult burns approximately 1,600–2,500 kilocalories (Calories) per day, depending on body size, age, sex, and activity level. This is called the Total Daily Energy Expenditure (TDEE). In joules, that equals roughly 6,700,000–10,500,000 J, or about 1.9–2.9 kWh — roughly the same as running a refrigerator for a day.
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All conversion results are provided for general informational purposes only. Our formulas use internationally recognized conversion factors; however, rounding may affect precision. Do not rely on these results for professional, medical, legal, or engineering decisions without independent verification. Read our full disclaimer.