Energy Conversion
Free energy conversion calculator: convert joules, kilojoules, megajoules, kilowatt-hours, calories, BTU, electronvolts, and more for physics and engineering.
About This Calculator
The Energy Conversion Calculator is a comprehensive online tool designed for students, engineers, scientists, and anyone who needs to convert between different energy units quickly and accurately. Whether you are working on physics problems, engineering calculations, chemistry experiments, or simply trying to understand your electricity bill, this converter supports 17 different energy units including the SI unit Joule (J), Kilojoule (kJ), Megajoule (MJ), Gigajoule (GJ), Watt-hour (Wh), Kilowatt-hour (kWh), Megawatt-hour (MWh), Calorie (cal), Kilocalorie (kcal), British Thermal Unit (BTU), Foot-pound (ft·lb), Electronvolt (eV), Kiloelectronvolt (keV), Megaelectronvolt (MeV), Therm, and Ton of TNT.
The conversion uses standard conversion factors: 1 kJ = 1,000 J, 1 MJ = 1,000,000 J, 1 kWh = 3,600,000 J, 1 BTU = 1,055.06 J, 1 cal = 4.184 J, 1 kcal = 4,184 J, 1 eV = 1.602176634 × 10⁻¹⁹ J, 1 therm = 105,500,000 J, and 1 ton of TNT = 4,184,000,000 J. The calculator applies the base unit (Joule) conversion method: it first converts the input value to Joules, then divides by the target unit's factor to get the result. A detailed breakdown table shows the equivalent value in every supported unit.
Regional Notes
India (IN): The SI units Joule, Kilojoule, and Megajoule are standard in scientific and engineering education. Kilowatt-hours (kWh) are used by electricity utilities (e.g., NTPC, state electricity boards) for billing. The Calorie is used in food packaging and nutrition labeling.
United States (US): BTU is widely used for heating, ventilation, and air conditioning (HVAC) systems and appliance ratings. Kilowatt-hours are used for electricity billing by utility companies. Foot-pounds are used in mechanical engineering contexts. Therms are used for natural gas billing.
United Kingdom (UK): Kilowatt-hours are the standard unit for electricity and gas billing (Ofgem). Therms are historically used for natural gas. The Joule is standard in scientific education. Calories are used in food labeling alongside kilojoules (dual labeling required by EU/UK regulations).
Frequently Asked Questions
What energy units does this converter support?
This energy converter supports the Joule (J), Kilojoule (kJ), Megajoule (MJ), Gigajoule (GJ), Watt-hour (Wh), Kilowatt-hour (kWh), Megawatt-hour (MWh), Calorie (cal), Kilocalorie (kcal), BTU, Foot-pound (ft·lb), Electronvolt (eV), Millielectronvolt (meV), Kiloelectronvolt (keV), Megaelectronvolt (MeV), Therm, and Ton of TNT. These units cover physics, engineering, chemistry, nutrition, and everyday energy measurements for users worldwide.
How do I convert between different energy units?
Enter your energy value in the input field, select the unit you are converting from in the 'From' dropdown, and select the target unit in the 'To' dropdown. Click 'Convert' to instantly see the converted value. The breakdown table shows the equivalent value in all supported energy units, and the chart visualizes the comparison between units. Each time you convert, the URL updates so you can share your exact conversion with others.
Is the energy conversion calculator free to use?
Yes, this energy converter is completely free to use with no limits on conversions. You can convert between any of the 17 supported energy units as many times as you need. There are no registration requirements, subscription fees, or usage limits. Simply enter your value and get instant results.
What is the difference between a calorie and a kilocalorie?
One kilocalorie (kcal) equals 1,000 calories (cal). In food and nutrition contexts, when people say 'calories' they usually mean kilocalories. Scientifically, 1 kcal = 4,184 J, while 1 cal = 4.184 J. This converter supports both units so you can accurately convert between food energy (kcal) and scientific energy (J) measurements.
How do you convert between BTU and Joules?
One British Thermal Unit (BTU) equals approximately 1,055.06 Joules. The BTU is commonly used in the United States and UK for heating and cooling systems, while the Joule is the SI standard unit. To convert BTU to Joules, multiply the BTU value by 1,055.06. To convert Joules to BTU, divide the Joule value by 1,055.06.
How is electricity energy measured in kilowatt-hours?
One kilowatt-hour (kWh) equals 3.6 million Joules (3.6 MJ). It represents the energy consumed by a 1,000-watt device running for one hour. Utility companies worldwide bill electricity in kWh. For example, a 100-watt light bulb running for 10 hours consumes 1 kWh of energy.
What are the most commonly used energy units in different countries?
In the United States, BTU is commonly used for heating and cooling systems, and kWh for electricity billing. In the UK, kWh is standard for electricity and gas billing, while therms are used for natural gas. In India (IN) and most other countries, the SI unit Joule and its multiples (kJ, MJ, GJ) are used in scientific contexts, while kWh is used for electricity billing. This converter supports all these units for international use.
What is an electronvolt and when is it used?
An electronvolt (eV) is the energy gained or lost by an electron moving through an electric potential difference of one volt. One eV equals approximately 1.602 × 10^(-19) Joules. Electronvolts are used in physics and chemistry to describe atomic-scale energies, such as ionization energies, bond energies, and particle physics. Common multiples include keV (1,000 eV) and MeV (1,000,000 eV).