Energy Converter

Convert between Joule, Calorie, kWh, BTU and more

Free online energy unit converter supporting 8 units: Joule (J), Kilojoule (kJ), Calorie (cal), Kilocalorie (kcal), Watt-hour (Wh), Kilowatt-hour (kWh), Electronvolt (eV), BTU. Real-time conversion with high precision. No registration required.

How to Use

Simple 3-step process to convert energy units:

Step 1: Enter Value
Enter the energy value in any unit field (Joule, Calorie, kWh, BTU, etc.)
Step 2: Automatic Conversion
All other unit fields will be automatically converted in real-time
Step 3: Copy Results
Copy the converted values you need for your calculations

All conversions are performed in your browser. No data is sent to our servers.

Energy Converter Tool

Joule (J)

Kilojoule (kJ)

Calorie (cal)

Kilocalorie (kcal)

Watt-hour (Wh)

Kilowatt-hour (kWh)

Electronvolt (eV)

British Thermal Unit (BTU)

Practical Use Cases

Energy converters are essential in various fields:

1. Electricity Bill Analysis

Convert kilowatt-hours (kWh) from your electricity bill to Joules or Calories to understand your actual energy consumption. 1 kWh = 3.6 million Joules = 860 kilocalories.

2. Food and Nutrition

Convert food energy from Calories (kcal) to Joules or kWh. A 100 kcal snack = 418.4 kJ = 0.116 Wh, helping you understand nutritional energy content.

3. Physics and Engineering

Convert energy units in scientific calculations. Electronvolts (eV) are commonly used in particle physics, while Joules are the SI standard unit.

4. HVAC and Heating

Convert BTU (British Thermal Units) to kWh for heating/cooling system specifications. 1 BTU = 0.000293 kWh, essential for HVAC system comparisons.

5. Renewable Energy

Compare solar panel output in kWh with battery capacity in Wh or Joules. Convert between units to calculate system efficiency and storage requirements.

What is Energy Conversion?

Energy is the capacity to do work. Different fields use different units to measure energy, making conversion essential.

Common Energy Units

Joule (J) is the SI unit of energy. 1 Joule = energy needed to move 1 Newton force over 1 meter. Calorie (cal) is used in nutrition (1 cal = 4.184 J). Kilowatt-hour (kWh) is used for electricity (1 kWh = 3.6 MJ). BTU is used in HVAC systems (1 BTU = 1055 J).

Why Convert Energy Units?

Different industries and countries use different energy units. Engineers need Joules, nutritionists use Calories, electricians use kWh, and HVAC technicians use BTU. Converting between these units ensures accurate calculations and communication.

Conversion Accuracy

This converter uses internationally recognized conversion factors: 1 cal = 4.184 J (thermochemical calorie), 1 kWh = 3,600,000 J, 1 BTU = 1055.06 J, 1 eV = 1.602176634×10⁻¹⁹ J. Results are provided with high precision for scientific and engineering applications.

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Frequently Asked Questions

What is the difference between Joule and Calorie?

Joule (J) is the SI unit of energy used in physics and engineering. Calorie (cal) is primarily used in nutrition and food energy. 1 calorie = 4.184 Joules. The 'Calorie' on food labels is actually a kilocalorie (kcal), which equals 1000 calories or 4184 Joules.

How do I convert kWh to Joules?

Multiply kilowatt-hours by 3,600,000. For example: 1 kWh = 3,600,000 J (3.6 MJ). This is because 1 kW = 1000 W, and 1 hour = 3600 seconds, so 1 kWh = 1000 × 3600 = 3,600,000 Watt-seconds = 3,600,000 Joules.

What is BTU used for?

BTU (British Thermal Unit) is commonly used in HVAC, heating, and cooling systems, especially in the United States. It represents the energy needed to heat 1 pound of water by 1°F. Air conditioners and heaters are often rated in BTU/hour. 1 BTU ≈ 1055 Joules.

How accurate is this energy converter?

This converter uses standard international conversion factors and provides results with up to 10 decimal places. For scientific work: 1 cal = 4.184 J (exact), 1 kWh = 3,600,000 J (exact), 1 BTU = 1055.06 J (ISO), 1 eV = 1.602176634×10⁻¹⁹ J (CODATA 2019).

Can I convert food Calories to kWh?

Yes. Food Calories (with capital C) are kilocalories. 1 kcal = 0.001163 kWh. For example, a 2000 kcal diet = 2.326 kWh per day. This comparison shows human daily energy consumption is equivalent to running a 100W light bulb for 23 hours.

What is an Electronvolt (eV)?

Electronvolt (eV) is a unit of energy used in atomic and particle physics. It's the energy gained by an electron moving through 1 volt of electric potential. 1 eV = 1.602176634×10⁻¹⁹ Joules. It's very small but convenient for describing atomic-scale energies.

Why are there different types of calories?

The 'calorie' has several definitions: thermochemical calorie (4.184 J), International Table calorie (4.1868 J), and 15°C calorie (4.1855 J). This converter uses the thermochemical calorie (4.184 J), which is the most common standard in modern nutrition and chemistry.

How do I calculate my home's energy consumption?

Check your electricity meter for kWh usage. To convert to other units: 1 kWh = 3.6 MJ = 860 kcal = 3412 BTU. For example, 500 kWh/month = 1,800 MJ = 430,000 kcal = 1,706,000 BTU. This helps compare with heating fuel costs measured in BTU.