Energy Converter
Convert between common energy units instantly. Ideal for physics, nutrition, engineering, and electricity billing calculations.
How to Use the Energy Converter
Converting between energy units is quick and accurate:
- Enter a numeric value in the input field. Decimals and scientific notation values are supported.
- Select the source unit from the dropdown (Joules, Calories, kWh, BTU, etc.).
- View all conversions in the results table. Calculations happen instantly as you type.
- Click Copy next to any result to copy the value to your clipboard.
About Energy Units
Energy is the capacity to do work and is one of the most fundamental concepts in physics. The SI unit of energy is the Joule (J), named after James Prescott Joule. One Joule equals the work done by a force of one Newton moving an object one meter. In nutrition, energy is measured in kilocalories (often labeled simply as "Calories" on food packaging), where 1 kcal = 4,184 J.
Electricity consumption is measured in kilowatt-hours (kWh), where 1 kWh = 3,600,000 J. The British Thermal Unit (BTU) is used in HVAC and heating industries. Electronvolts (eV) are used in atomic and particle physics. Understanding energy unit conversions is vital for comparing fuel sources, calculating electricity costs, managing nutrition, and engineering design.
Common Energy Conversions
The table below provides a quick reference for frequently needed energy conversions across nutrition, electricity, and heating applications.
| From | To | Result |
|---|---|---|
| 1 calorie (cal) | Joules | 4.184 J |
| 1 kilocalorie (kcal) | Kilojoules | 4.184 kJ |
| 1 kWh | Joules | 3,600,000 J |
| 1 kWh | BTU | 3,412.14 BTU |
| 1 kWh | Kilocalories | 860.42 kcal |
| 1 BTU | Joules | 1,055.06 J |
| 2,000 kcal (daily diet) | Kilojoules | 8,368 kJ |
| 2,000 kcal (daily diet) | kWh | 2.324 kWh |
| 1 foot-pound | Joules | 1.3558 J |
Energy Conversion Formulas
Energy conversions use the Joule (J) as the SI base unit. The key relationships and formulas are listed below with worked examples to demonstrate step-by-step calculations.
Calories to Joules: J = cal × 4.184
Kilocalories to Kilojoules: kJ = kcal × 4.184
kWh to Joules: J = kWh × 3,600,000
kWh to BTU: BTU = kWh × 3,412.14
BTU to Joules: J = BTU × 1,055.06
Joules to Calories: cal = J ÷ 4.184
Worked Examples
- Convert 500 kcal (food Calories) to kJ: kJ = 500 × 4.184 = 2,092 kJ
- Convert 10 kWh to BTU: BTU = 10 × 3,412.14 = 34,121.4 BTU
- Convert 50,000 BTU to kWh: kWh = 50,000 ÷ 3,412.14 = 14.65 kWh
- Convert 100 kJ to kilocalories: kcal = 100 ÷ 4.184 = 23.9 kcal
When You Need This Converter
Energy conversion is essential across nutrition, utilities, engineering, and science. Here are the most common situations where this tool proves valuable:
- Nutrition and Diet: Food labels in the US list energy in Calories (kilocalories), while many other countries use kilojoules (kJ). Converting between kcal and kJ is essential for comparing food labels internationally. A 2,000 kcal daily diet equals 8,368 kJ. Many fitness apps and nutritional databases require conversion between these units.
- Electricity and Utility Bills: Electricity is billed in kilowatt-hours (kWh). Understanding how many kWh an appliance uses helps estimate costs. A 1,500-watt space heater running for 8 hours uses 12 kWh. Converting kWh to BTU helps compare heating options between electric and gas systems.
- HVAC and Home Heating: Heating and cooling systems are rated in BTU. Air conditioners, furnaces, and heat pumps all specify capacity in BTU/hour. Converting between BTU and kWh helps homeowners compare energy costs between electric and gas-powered heating systems.
- Physics and Engineering: Scientists and engineers use Joules and kilojoules as standard energy units. Converting between Joules, calories, and electronvolts is a daily task in chemistry, thermodynamics, and particle physics research. Understanding energy equivalences is fundamental to designing efficient systems.
Frequently Asked Questions
One thermochemical calorie equals exactly 4.184 Joules. To convert Joules to calories, divide by 4.184. Note that food "Calories" (capital C) are actually kilocalories (1 kcal = 4,184 J).
A calorie (cal, lowercase) is a small unit of energy equal to 4.184 Joules. A Calorie (Cal, uppercase) used on food labels is actually a kilocalorie (kcal), equal to 1,000 small calories or 4,184 Joules.
Multiply kilowatt-hours by 3,412.14 to get BTU. For example, 1 kWh = 3,412.14 BTU. This conversion is commonly used in HVAC and energy billing.
An electronvolt (eV) is the energy gained by a single electron moving through an electric potential difference of one volt. It equals 1.602 × 10⁻¹⁹ Joules and is commonly used in particle physics and chemistry.
Multiply the number of calories by 4.184 to get Joules. For kilocalories (food Calories), multiply by 4,184. For example, 100 kcal = 100 × 4,184 = 418,400 Joules (418.4 kJ).
The average cost of 1 kWh varies by location. In the United States, the average residential electricity rate is approximately $0.16 per kWh (as of 2025). Rates vary significantly by state and country.
Energy is the total amount of work done, measured in Joules or kWh. Power is the rate at which energy is used, measured in Watts (Joules per second). A 100-watt light bulb running for 10 hours uses 1 kWh of energy (100 W × 10 h = 1,000 Wh = 1 kWh).
A general rule of thumb is 20 BTU per square foot. A 300 sq ft room would need approximately 6,000 BTU. Factors like insulation, climate, ceiling height, and windows affect the actual requirement. 1 BTU equals 1,055.06 Joules.