Energy Converter

Q: What is the difference between a calorie and a Calorie?

A lowercase calorie (cal) is the 'small calorie' - the energy needed to raise 1 gram of water by 1°C. An uppercase Calorie (Cal) or kilocalorie (kcal) is the 'food calorie' - equal to 1000 small calories. Food nutrition labels use kilocalories (kcal), often written as 'Calories' with capital C.

Instantly convert between 12+ energy units including Joules, Calories, BTU, kWh, eV, and more. Features real-time conversion, practical examples, and scientific notation support.

Free to useNo sign-up requiredUpdated Feb 2026

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100 kcal (banana) 1 kWh (electricity) 12,000 BTU (AC unit) 1 Therm (natural gas)

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⚡ J Joule

Scientific Notation

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About Energy Converter

Welcome to the Energy Converter, the most comprehensive and user-friendly tool for converting between energy units. Whether you are a physicist calculating particle energies, an engineer designing HVAC systems, a nutritionist tracking caloric intake, or a homeowner understanding electricity bills, this converter provides instant, accurate conversions across 12 different energy units.

Supported Energy Units

This converter supports the most commonly used energy units across science, engineering, and everyday life:

Unit	Symbol	Equivalent in Joules	Common Use
Joule	J	1 J	Physics, SI standard
Kilojoule	kJ	1,000 J	Food energy, chemistry
Calorie	cal	4.184 J	Chemistry, small-scale heat
Kilocalorie	kcal	4,184 J	Nutrition, food labels
British Thermal Unit	BTU	1,055.06 J	HVAC, heating systems
Watt-hour	Wh	3,600 J	Batteries, small appliances
Kilowatt-hour	kWh	3,600,000 J	Electricity billing
Foot-pound	ft·lb	1.356 J	Mechanical work (US)
Electronvolt	eV	1.602 × 10⁻¹⁹ J	Atomic/particle physics
Mega-electronvolt	MeV	1.602 × 10⁻¹³ J	Nuclear physics
Erg	erg	10⁻⁷ J	CGS system, astrophysics
Therm	thm	105,505,600 J	Natural gas billing

Understanding Energy Units

The Joule - SI Unit of Energy

The Joule (J) is the standard SI unit of energy, named after physicist James Prescott Joule. One Joule equals:

The work done when a force of 1 newton moves an object 1 meter
The energy dissipated as heat when 1 ampere flows through 1 ohm for 1 second
One watt of power for one second (1 W·s)

Joule Definition

$$1 \text{ J} = 1 \text{ N} \cdot \text{m} = 1 \text{ kg} \cdot \frac{\text{m}^2}{\text{s}^2} = 1 \text{ W} \cdot \text{s}$$

Calories vs Kilocalories

This is one of the most confusing aspects of energy units:

Small calorie (cal): The energy to raise 1 gram of water by 1°C. Used in chemistry and physics.
Large Calorie or kilocalorie (kcal): Equal to 1000 small calories. This is the "food calorie" on nutrition labels.

When food labels say "100 Calories," they actually mean 100 kilocalories (kcal) or 418,400 Joules.

Calorie Conversions

$$1 \text{ cal} = 4.184 \text{ J}$$ $$1 \text{ kcal} = 1000 \text{ cal} = 4184 \text{ J}$$

BTU - British Thermal Unit

The BTU measures heat energy and is widely used in the United States for heating, ventilation, and air conditioning (HVAC) systems. One BTU is the energy needed to raise 1 pound of water by 1°F.

BTU Conversion

$$1 \text{ BTU} = 1055.06 \text{ J} \approx 252 \text{ cal}$$

Kilowatt-hour - Electricity Unit

The kilowatt-hour (kWh) is the standard unit for measuring electricity consumption. It represents using 1000 watts of power for one hour.

Kilowatt-hour Conversion

$$1 \text{ kWh} = 1000 \text{ W} \times 3600 \text{ s} = 3,600,000 \text{ J} = 3.6 \text{ MJ}$$

Electronvolt - Particle Physics Unit

The electronvolt (eV) is the energy gained by an electron accelerating through 1 volt. Though tiny in everyday terms, it is the natural unit for atomic and particle physics.

Electronvolt Conversion

$$1 \text{ eV} = 1.602176634 \times 10^{-19} \text{ J}$$

Real-World Applications

🍎

Nutrition & Fitness

Track food energy in kilocalories (kcal) and understand how exercise burns energy. Running 1 mile burns approximately 80-100 kcal.

🔌

Electricity Bills

Understand your energy consumption in kWh. Average US home uses about 30 kWh daily, costing roughly 10-15 cents per kWh.

🌡️

HVAC Systems

Size heating and cooling equipment in BTU. A small room AC typically provides 5,000-8,000 BTU/hour of cooling capacity.

⚛️

Physics Research

Measure particle energies in eV and MeV. The Large Hadron Collider accelerates protons to 6.5 TeV (tera-electronvolts).

🏠

Natural Gas

Natural gas is often billed in therms. One therm equals about 100,000 BTU or roughly 29.3 kWh of heat energy.

🔋

Battery Capacity

Battery energy is measured in Wh or kWh. A typical smartphone battery holds about 10-15 Wh, while electric car batteries range from 40-100 kWh.

How to Use This Converter

Select source unit: Click on the energy unit you want to convert from in the grid.
Enter value: Type your number in the input field. Decimals and large numbers are supported.
View results: All conversions appear instantly in the results grid below.
Toggle scientific notation: For very large or small numbers, enable scientific notation for cleaner display.
Copy results: Click the copy button on any result, or "Copy All" to get all conversions.

Conversion Formulas

All conversions use the Joule as the base unit. To convert from unit A to unit B:

General Conversion Formula

$$\text{Value in B} = \text{Value in A} \times \frac{\text{Factor}_A}{\text{Factor}_B}$$

Where Factor is the number of Joules per unit. For example, to convert 100 kcal to BTU:

Example: 100 kcal to BTU

$$100 \text{ kcal} = 100 \times \frac{4184}{1055.06} \approx 396.6 \text{ BTU}$$

Frequently Asked Questions

What is a Joule?

The Joule (J) is the SI unit of energy. It equals the work done when a force of one newton moves an object one meter. One Joule also equals one watt-second of electrical energy. Named after physicist James Prescott Joule, it is used universally in physics and engineering.

What is the difference between a calorie and a Calorie?

A lowercase calorie (cal) is the "small calorie" - the energy needed to raise 1 gram of water by 1°C. An uppercase Calorie (Cal) or kilocalorie (kcal) is the "food calorie" - equal to 1000 small calories. Food nutrition labels use kilocalories (kcal), often written as "Calories" with capital C.

How do I convert BTU to Joules?

To convert BTU to Joules, multiply by 1055.06. One BTU (British Thermal Unit) equals approximately 1055.06 Joules. BTU measures the heat needed to raise 1 pound of water by 1°F and is commonly used for heating/cooling systems in the US.

What is a kilowatt-hour (kWh)?

A kilowatt-hour (kWh) is a unit of energy equal to using 1000 watts for one hour, or 3,600,000 Joules. It is the standard billing unit for electricity consumption. For example, a 100W light bulb running for 10 hours uses 1 kWh of electricity.

What is an electronvolt (eV)?

An electronvolt (eV) is the energy gained by an electron when accelerated through a potential difference of 1 volt. Equal to approximately 1.602 × 10⁻¹⁹ Joules, it is commonly used in atomic, nuclear, and particle physics where Joules would be inconveniently small.

How many calories are burned running a mile?

Running one mile burns approximately 80-100 kilocalories (food calories) for an average person, which equals about 335,000-420,000 Joules of energy. The exact amount varies based on body weight, running speed, and individual metabolism.

Additional Resources

Reference this content, page, or tool as:

"Energy Converter" at https://MiniWebtool.com/energy-converter/ from MiniWebtool, https://MiniWebtool.com/

by miniwebtool team. Updated: Feb 05, 2026

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