エネルギー
About Energy Conversion
Energy is the capacity to do work, one of the most fundamental concepts in physics and essential to understanding everything from nutrition to nuclear power. It appears in many forms—kinetic, potential, thermal, electrical, chemical, and nuclear—and can be converted from one form to another but never created or destroyed (conservation of energy).
Different fields use different energy units based on historical development and practical convenience: joules (J) in physics and engineering, calories in nutrition and chemistry, kilowatt-hours (kWh) for electricity billing, BTU (British Thermal Units) for heating and cooling in the US, and electronvolts (eV) in atomic and particle physics.
Our energy converter handles all common units across scientific, nutritional, and practical applications, making it easy to compare energy costs, understand food labels, or work through physics problems.
Common Energy Conversions
| 変換元 | 変換先 | 乗数 |
|---|---|---|
| ジュール | Calories (small) | 0.2390 |
| Calories (small) | ジュール | 4.184 |
| kWh | ジュール | 3,600,000 |
| ジュール | kWh | 2.778×10⁻⁷ |
| BTU | ジュール | 1,055 |
| kWh | BTU | 3,412 |
| kcal (food cal) | kJ | 4.184 |
| Watt-hours | ジュール | 3,600 |
| eV | ジュール | 1.602×10⁻¹⁹ |
| Therms | BTU | 100,000 |
Energy 単位リファレンス
Joule (J) – The SI単位 of energy, defined as 1 newton-meter or 1 watt-second. Named after James Prescott Joule. Used universally in physics and engineering for all energy calculations.
Kilojoule (kJ) – 1,000 joules. Common in nutrition labels outside the US (food energy is often shown in both kJ and kcal). 1 kcal = 4.184 kJ.
Calorie (cal) – Small calorie: the energy needed to heat 1 gram of water by 1°C. 1 cal = 4.184 J exactly (thermochemical calorie). Used in chemistry and physics.
Kilocalorie (kcal) – Food calorie: the energy to heat 1 kilogram of water by 1°C. 1 kcal = 4,184 J = 4.184 kJ. This is what nutrition labels call a "Calorie" (with capital C).
Kilowatt-hour (kWh) – Energy consumed by 1 kilowatt of power over 1 hour. The standard unit for electricity billing worldwide. 1 kWh = 3.6 MJ = 3,600,000 J exactly.
BTU (British Thermal Unit) – Energy needed to heat 1 pound of water by 1°F. Used for heating, cooling, and fuel content in the US. 1 BTU ≈ 1,055 J. Air conditioners are rated in BTU/hour.
Electronvolt (eV) – The energy gained by an electron accelerating through a potential difference of 1 volt. 1 eV = 1.602×10⁻¹⁹ J. Used in atomic, nuclear, and particle physics for its convenient scale.
Therm – Natural gas billing unit equal to 100,000 BTU ≈ 105.5 MJ. Used by gas utilities, especially in the US and UK.
もっと詳しく
Explore our in-depth guides on this topic:
関連記事
Nuclear vs Fossil Fuel Energy: Comparing Power Sources
Compare the energy density and output of nuclear versus fossil fuels—from uranium's incredible density to coal's widespread use.
続きを読むRenewable Energy Measurements: Solar, Wind, and More
Learn how renewable energy is measured—from solar panel wattage to wind turbine capacity factors and grid-scale storage.
続きを読むの歴史 Energy Measurement: 変換元 Horsepower to ジュール
Explore how humanity developed ways to measure energy—from James Watt's horsepower to the modern joule and calorie.
続きを読む