Energy Converter
Convert joules, calories (food & thermo), kWh, BTU, electronvolts, etc.
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*Diagram shows values relative to the selected base unit (Joule).
Unit Information
What are Joules (J)?
The joule (symbol: J) is the SI derived unit of energy, named after the English physicist James Prescott Joule. One joule is defined as the amount of work done when a force of one newton displaces an object by one meter in the direction of the force. It's a versatile unit used across all scientific disciplines to measure energy, work, and heat.
What are Food Calories (kcal)?
A food Calorie (with a capital C, also known as a kilocalorie or kcal) is a unit of energy commonly used to measure the energy content of food and beverages. One food Calorie (1 kcal) is the amount of heat needed to raise the temperature of one kilogram of water by one degree Celsius. It is equivalent to 1000 'small' calories (thermochemical calories) or 4184 joules.
What are Kilowatt-hours (kWh)?
A kilowatt-hour is a unit of energy equal to the energy consumed by a device with a power of one kilowatt operating for one hour. It is commonly used by utility companies for billing electricity consumption.
What are British Thermal Units (BTU)?
A British Thermal Unit (BTU) is a traditional unit of heat energy. It is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. It's often used to rate the power of heating and cooling systems (as BTU/hour).
What are Electronvolts (eV)?
An electronvolt is a very small unit of energy used in atomic and particle physics. It's the amount of kinetic energy gained by a single electron when it accelerates through an electric potential difference of one volt. It is useful for describing the energy of photons and elementary particles.
Formulas
1 kcal (food Calorie) = 4184 J
To convert food Calories (kcal) to joules, multiply by 4184.
1 kWh = 3,600,000 J
A kilowatt-hour represents the energy consumed by a 1-kilowatt device running for one hour.
1 BTU ≈ 1055 J
One British Thermal Unit is approximately 1055 Joules.
1 cal (thermochemical) = 4.184 J
A small calorie is 4.184 Joules.
1 J ≈ 6.242 × 10¹⁸ eV
One Joule is an enormous amount of energy on the particle physics scale.
Key Reference Points
- Energy to lift a small apple (100g) by 1 meter: ~1 Joule.
- Daily energy intake for an average adult: ~2000-2500 kcal (8368-10460 kJ).
- A typical 100W light bulb running for 10 hours uses 1 kWh of energy.
- Energy released by burning 1 liter of gasoline: ~32-35 Megajoules (MJ).
- Energy released by a single lightning bolt: ~1-5 Gigajoules (GJ).
- One gram of carbohydrate: ~4 kcal.
- One gram of protein: ~4 kcal.
- One gram of fat: ~9 kcal.
- A can of soda (355ml): ~140 kcal.
- A slice of whole wheat bread: ~70-80 kcal.
Did You Know?
An electronVolt (eV) is a very small unit of energy, commonly used in atomic and particle physics. It's the amount of kinetic energy gained (or lost) by a single electron when it accelerates through an electric potential difference of one volt in a vacuum. 1 eV is approximately 1.602 × 10⁻¹⁹ joules.
The law of conservation of energy, a fundamental principle in physics, states that the total energy of an isolated system remains constant; it can only be transformed from one form to another.
The 'calorie' in physics (small 'c') is the energy to raise 1 gram of water by 1°C. The 'Calorie' in food (capital 'C') is a kilocalorie, 1000 times larger, the energy to raise 1 kilogram of water by 1°C.
Albert Einstein's famous equation shows that mass itself is a form of energy. The conversion factor, c² (the speed of light squared), is enormous, meaning a tiny amount of mass can be converted into a tremendous amount of energy, as demonstrated in nuclear reactions.
The Second Law of Thermodynamics states that the total entropy (a measure of disorder) of an isolated system can only increase over time. This implies that while energy is conserved, its quality degrades, becoming less useful for work as it spreads out as heat.
Photosynthesis is the process by which green plants use sunlight to convert carbon dioxide and water into glucose (chemical energy) and oxygen. It's one of the most important energy conversion processes on Earth.
A supernova, the explosion of a massive star, can briefly outshine an entire galaxy, releasing an incredible amount of energy—often more than 10⁴⁴ joules, which is more energy than our Sun will produce in its entire 10-billion-year lifetime.
An object's energy can be in the form of kinetic energy (energy of motion) or potential energy (stored energy). A roller coaster at the top of a hill has maximum potential energy, which converts to kinetic energy as it rushes down.
The energy released by large explosions is often measured in tons of TNT equivalent. One ton of TNT is defined as 4.184 gigajoules. This provides a standard way to compare the energy output of different explosive devices.
BMR is the amount of energy your body needs to maintain basic life-sustaining functions while at rest. It's often expressed in kilocalories (Calories) or kilojoules per day.
Energy density is the amount of energy stored in a given system or region of space per unit volume or mass. For example, gasoline has a much higher energy density by mass than lithium-ion batteries, which is a major challenge for electric vehicles.
The erg is the unit of energy in the CGS (centimeter–gram–second) system. It is equal to 10⁻⁷ joules. It's a very small unit, roughly the amount of work done by a common housefly performing a single 'push-up'.
Energy sources are broadly classified as renewable (like solar, wind, and hydro, which are naturally replenished) and non-renewable (like fossil fuels, which are finite).
A therm is a non-SI unit of heat energy, equal to 100,000 BTU. It is still used in some countries for pricing natural gas.
A bomb calorimeter is a device used to measure the energy content of food or fuel. It works by burning the substance in a sealed container surrounded by water and measuring the resulting temperature increase of the water.
The foot-pound (ft·lbf) is a unit of work or energy in the imperial system. It is the energy transferred upon applying a force of one pound-force through a linear displacement of one foot.
In cosmology, dark energy is a mysterious form of energy that is hypothesized to permeate all of space and is responsible for the accelerating expansion of the universe. It is estimated to make up about 68% of the total energy in the universe.
A 'quad' is a unit of energy equal to one quadrillion (10¹⁵) BTU. It is used in energy statistics to discuss large-scale national or global energy budgets.