Energy Converter

Convert between different units of energy - joules, calories, kilocalories, BTU, watt-hours, and more.

Result: 0.0000e+0

What It Does

An Energy Converter is a versatile tool for converting between different units of energy measurement. It converts between scientific units like joules (J) and kilojoules (kJ), nutritional units like calories (cal) and kilocalories (kcal), electrical units like watt-hours (Wh) and kilowatt-hours (kWh), thermal units like BTU (British Thermal Units), and specialized units like electron-volts (eV) and foot-pounds (ft·lb). This tool is essential for nutrition (food energy), physics (work and heat), electricity (energy consumption), engineering (energy systems), and scientific research. It provides accurate conversions with support for both small-scale (electron-volts) and large-scale (kilowatt-hours) energy measurements. Perfect for understanding food labels, calculating electricity bills, physics problems, and any energy-related calculations.

Key Features:

  • Convert between 9 common energy units (joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, electron-volts, foot-pounds)
  • Real-time conversion as you type - instant results
  • Swap button to quickly reverse conversion direction
  • High precision results with scientific notation for very small/large values
  • Nutritional energy: calories and kilocalories for food
  • Electrical energy: watt-hours and kilowatt-hours for electricity
  • Scientific units: joules and electron-volts for physics
  • Mobile-responsive design for on-the-go conversions

How To Use

Convert energy values instantly between different units. Perfect for nutrition, physics, electricity, and scientific applications.

1

Enter the Energy Value

Type or paste the energy value you want to convert into the "Value" input field. You can enter whole numbers or decimals (e.g., 100, 2500.5, 0.001).

2

Select Source Unit

Choose the unit you're converting FROM using the "From" dropdown. Options include joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, electron-volts, and foot-pounds.

3

Select Target Unit

Choose the unit you want to convert TO using the "To" dropdown. The result updates automatically as you make your selection.

4

View Result

See the converted energy value displayed prominently in the result box. Very small or large values may be shown in scientific notation for readability.

5

Swap Units (Optional)

Click the swap button (⇄) to instantly reverse the conversion direction, swapping the "From" and "To" units without re-entering the value.

Pro Tips

  • •1 calorie (cal) = 4.184 joules
  • •1 kilocalorie (kcal) = 1,000 calories = 4,184 joules (this is the "Calorie" on food labels)
  • •1 kilowatt-hour (kWh) = 3,600,000 joules = 860.421 kilocalories
  • •1 BTU = 1,055.06 joules = 252.164 calories
  • •Food labels show "Calories" which are actually kilocalories (kcal)
  • •Electricity bills use kilowatt-hours (kWh)
  • •Electron-volts are extremely small units used in particle physics

Benefits

Nutrition: Convert food energy between calories and kilojoules for international labels
Electricity: Understand energy consumption in different units
Physics: Convert energy measurements for scientific calculations
Engineering: Convert energy units for system design and analysis
Education: Learn energy relationships and unit conversions
Accuracy: Eliminate manual calculation errors in energy conversions
Time Saving: Instant conversions save time over manual calculations
Versatility: Handle everything from tiny electron-volts to large kilowatt-hours

Use Cases

Nutrition and Food Labels

Convert food energy between calories and kilojoules. Food labels in different countries use different units, and this converter helps compare nutritional information.

Convert 250 kilocalories (food label) to kilojoules (1,046 kJ) for international comparison

Electricity Bills and Consumption

Convert electrical energy consumption between different units. Electricity bills use kilowatt-hours, but you may need to convert to other units for calculations.

Convert 100 kWh electricity usage to joules (360,000,000 J) for energy calculations

Physics and Scientific Research

Convert energy measurements in physics experiments and calculations. Scientists work with joules, electron-volts, and other units depending on the application.

Convert 1 electron-volt to joules (1.602 × 10⁻¹⁹ J) for particle physics calculations

Exercise and Fitness

Convert exercise energy expenditure between calories and kilojoules. Fitness trackers and exercise equipment may use different units.

Convert 500 calories burned to kilojoules (2,092 kJ) for fitness tracking

Heating and Cooling

Convert thermal energy between BTU and other units. HVAC systems and heating equipment often use BTU for energy ratings.

Convert 10,000 BTU to kilowatt-hours (2.93 kWh) for heating system calculations

Frequently Asked Questions

1 What is the difference between a calorie and a Calorie?
A lowercase "calorie" (cal) is a small unit equal to 4.184 joules. An uppercase "Calorie" (Cal) on food labels is actually a kilocalorie (kcal), equal to 1,000 calories or 4,184 joules. This capitalization convention was adopted to make food labels more readable, but it causes confusion. When you see "200 Calories" on a food label, it means 200 kilocalories (200,000 calories). Our converter uses "calorie" for the small unit and "kilocalorie" for the food energy unit.
2 How do I convert kilowatt-hours to calories?
One kilowatt-hour (kWh) equals 860.421 kilocalories (the "Calories" on food labels). To convert: multiply kWh by 860.421. For example, 1 kWh × 860.421 = 860.421 kcal. This means the energy in 1 kWh of electricity is equivalent to about 860 food calories. Conversely, to convert calories to kWh: divide by 860.421.
3 What is a BTU and when is it used?
BTU stands for "British Thermal Unit" and is a unit of energy commonly used in the United States for heating and cooling systems. One BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. BTUs are used for air conditioners, furnaces, water heaters, and other HVAC equipment. One BTU equals 1,055.06 joules or 252.164 calories.
4 What are electron-volts used for?
Electron-volts (eV) are extremely small energy units used in particle physics, atomic physics, and quantum mechanics. One electron-volt is the energy gained by an electron moving through an electric potential difference of one volt. One eV equals 1.602 × 10⁻¹⁹ joules. Electron-volts are convenient for atomic-scale energies because typical atomic and molecular energies are in the range of a few to thousands of electron-volts. For example, visible light photons have energies of 1.6-3.3 eV.
5 How accurate are energy conversions?
Energy conversions use precise conversion factors based on international standards. For example, 1 calorie = 4.184 joules exactly (by definition since 1948). Results are displayed with appropriate precision: standard notation for normal values, scientific notation for very small (electron-volts) or very large values. The precision is sufficient for all practical applications including nutrition, physics, and engineering.
6 Why do food labels use different energy units in different countries?
Food labels use different units based on regional conventions. The United States uses "Calories" (kilocalories), while many other countries use kilojoules (kJ). The European Union requires both units on labels. One kilocalorie equals 4.184 kilojoules. This converter helps compare nutritional information across different labeling systems and understand energy content regardless of the unit used.

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