Energy Converter
Convert between units of energy including joules, calories, watt-hours, kilowatt-hours, and BTU. Essential for physics, nutrition, engineering, and various technical applications.
Convert Energy Units
Enter an energy value and select the units to convert between:
1 kcal = 4,184 J โข 1 kWh = 3,600,000 J โข 1 BTU โ 1,055 J
Understanding Energy Units
Energy is the capacity to do work or produce heat. Different fields use different energy units depending on their specific applications and measurement traditions.
Energy Unit Systems
โก SI Units (International System)
Joule (J): Base unit of energy
Kilojoule (kJ): 1,000 joules
Work = Force ร Distance
Used in physics and science
Universal standard
๐ Thermal/Caloric Units
Calorie (cal): Heat energy
Kilocalorie (kcal): Food calories
1 kcal = 1 Calorie on food labels
Used in nutrition and dietetics
Based on water heating
๐ Electrical Units
Watt-hour (Wh): Electrical energy
Kilowatt-hour (kWh): Electricity billing
Power ร Time = Energy
Used for electricity consumption
Standard for utility billing
Complete Energy Conversion Table
| Unit | Symbol | Joules | Description |
|---|---|---|---|
| Joule | J | 1 | SI base unit of energy |
| Kilojoule | kJ | 1,000 | Common in scientific calculations |
| Calorie | cal | 4.184 | Thermochemical calorie |
| Kilocalorie | kcal | 4,184 | Food calorie (nutrition) |
| Watt-hour | Wh | 3,600 | Electrical energy consumption |
| Kilowatt-hour | kWh | 3,600,000 | Electricity billing unit |
| British Thermal Unit | BTU | 1,055 | Heating and cooling capacity |
| Foot-pound | ftยทlbf | 1.356 | Mechanical work |
| Erg | erg | 0.0000001 | CGS system unit |
| Electron volt | eV | 1.602 ร 10^-19 | Atomic and particle physics |
| Therm | therm | 105,506,000 | 100,000 BTU (natural gas) |
Common Energy Values
| Item | Energy | Description |
|---|---|---|
| Apple (medium) | 52 kcal | 182g apple |
| Slice of Bread | 79 kcal | White bread slice |
| 100W Light Bulb (1 hour) | 100 Wh | Electrical consumption |
| Household Electricity (month) | 300 kWh | Average US usage |
| Gallon of Gasoline | 33.7 kWh | Chemical energy content |
| Chocolate Bar | 230 kcal | Milk chocolate (45g) |
| Air Conditioner (1 hour) | 1,000 BTU | Window unit capacity |
| Banana | 105 kcal | Medium banana |
| LED TV (1 hour) | 50 Wh | 55-inch 4K display |
| Human Basal Metabolism | 1,800 kcal/day | Daily resting energy |
Nutrition and Food Energy
๐ Calorie Definition
1 calorie = 4.184 joules
Heat to raise 1g water by 1ยฐC
Food labels use kilocalories
1 kcal = 1 Calorie (capital C)
Used for nutritional energy
๐ฅ Macronutrient Calories
Carbohydrates: 4 kcal/g
Proteins: 4 kcal/g
Fats: 9 kcal/g
Alcohol: 7 kcal/g
Fiber: 2 kcal/g
Different energy densities
๐ Daily Energy Needs
Sedentary: 1,800-2,000 kcal
Lightly active: 2,200 kcal
Moderately active: 2,400 kcal
Very active: 2,800 kcal
Extremely active: 3,200+ kcal
Varies by age, gender, activity
Electrical Energy
๐ก Watt-hour vs Kilowatt-hour
1 Wh = 1 watt ร 1 hour
1 kWh = 1,000 watt-hours
Electricity billing unit
Power ร Time = Energy
Common for appliances
๐ Home Electricity Usage
Refrigerator: 100-200 kWh/month
Air conditioning: 500-1,000 kWh/month
Water heating: 300-500 kWh/month
Lighting: 50-100 kWh/month
Varies by usage and efficiency
โก Power vs Energy
Power = Energy/Time (watts)
Energy = Power ร Time (watt-hours)
Rate vs total amount
Instantaneous vs accumulated
Important distinction
Thermal Energy
๐ฅ BTU and Heating
1 BTU = heat for 1ยฐF rise in 1 lb water
Used in HVAC industry
Heating capacity ratings
Air conditioner sizing
US customary unit
๐ญ Industrial Applications
Steam energy calculations
Process heating requirements
Fuel energy content
Thermal efficiency
Energy balance equations
๐ก๏ธ Temperature vs Energy
Temperature: heat intensity
Energy: total heat content
Specific heat capacity
Phase changes
Mass ร specific heat ร ฮT
Physics and Scientific Applications
โ๏ธ Atomic Physics
Electron volt (eV)
1 eV = 1.602 ร 10^-19 J
Atomic energy levels
Particle accelerator energies
Quantum mechanical calculations
๐ Astrophysics
Stellar energy output
Solar radiation
Cosmic energy scales
Black hole thermodynamics
Large energy magnitudes
๐ฌ Laboratory Work
Calorimetry experiments
Heat transfer studies
Thermodynamic calculations
Chemical reaction energies
Material science testing
๐ Energy Tip: Remember that power is the rate of energy transfer (watts), while energy is the total amount (watt-hours). A 100-watt light bulb uses 100 joules of energy every second, or 100 watt-hours in one hour.