What is the Energy Converter?

The Energy Converter is a powerful tool that helps you convert between different units of energy measurement. Whether you're working with Joules, Calories, Kilowatt-hours, or BTUs, this converter provides instant and accurate results for scientific, engineering, and everyday applications.

Privacy First: All calculations are performed entirely in your browser. No data is sent to any server, and nothing is stored or tracked. Your input values remain completely private.

Who Needs This Tool?

Nutritionists & Fitness

Convert between calories and kilojoules on food labels for accurate dietary planning.

Homeowners

Understand electricity bills in kWh or gas bills in therms/BTU for better energy management.

Engineers

Work with mechanical, electrical, or thermal energy systems requiring precise conversions.

HVAC Professionals

Calculate heating and cooling requirements in BTU for system design and installation.

Scientists & Students

Perform energy calculations in physics and chemistry with multiple unit systems.

Electricians

Convert between watt-hours and joules for electrical system calculations.

Supported Units

The converter supports a comprehensive range of 24 energy units across multiple measurement systems:

Metric (Joule)

SI base unit and multiples

Joule (J)
Kilojoule (kJ)
Megajoule (MJ)
Gigajoule (GJ)

Calorie

Food and nutrition energy

Calorie (cal)
Kilocalorie (kcal)
Food Calorie (Cal)

Electrical

Power consumption units

Watt-hour (Wh)
Kilowatt-hour (kWh)
Megawatt-hour (MWh)

Thermal (BTU)

Heating and cooling energy

British Thermal Unit (BTU)
Therm
Quad

Atomic (Electronvolt)

Particle physics energy

Electronvolt (eV)
Kiloelectronvolt (keV)
Megaelectronvolt (MeV)
Gigaelectronvolt (GeV)

Mechanical & Other

Work and specialized units

Foot-pound (ft·lbf)
Inch-pound (in·lbf)
Erg
Horsepower-hour (HPh)
Tonne of Oil Equivalent (toe)
Tonne of Coal Equivalent (tce)

How to Use the Energy Converter

Basic Conversion

Enter a Value

Type your number in the input field. Numbers are automatically formatted with thousand separators for easy readability (e.g., 3,600,000).

Select Source Unit

Choose your starting unit from the dropdown menu. You can type to search for a specific unit quickly.

View Instant Results

Results appear immediately below in all enabled units. No button clicks required—conversions update in real-time as you type.

Customizing Your Experience

Adjust Decimal Precision

Use the "Decimals" dropdown to control how many decimal places are shown. Choose from 2, 4, 6, 8 decimals, or select "Auto" to let the tool decide based on the value.

Show/Hide Units

Click "Customize Units" to toggle which units appear in your results. Perfect for users who regularly work with specific unit groups like metric or thermal.

Copy Results

Click on any result row to copy that specific value. For multiple values, use the "Copy All Results" button to copy everything at once in a clean format.

Quick Reference

Not sure about a unit? Click "Unit Reference" to see a table explaining each unit, its value relative to Joule, and common use cases.

Tips for Common Conversions

Quick Reference Values:

Food energy: 1 kcal (food Calorie) = 4.184 kJ
Electricity: 1 kWh = 3.6 MJ = 3,600,000 J
Heating: 1 BTU ≈ 1,055 J ≈ 0.293 Wh
Natural gas: 1 therm = 100,000 BTU ≈ 29.3 kWh

Features

Instant Conversion

Results update in real-time as you type. No need to click a button or wait for processing—just enter your value and see all conversions immediately.

Comprehensive Unit Support

Convert between 24 different energy units spanning scientific, electrical, thermal, and everyday measurement systems. From Joules to BTU, from calories to kilowatt-hours.

Smart Input Formatting

Large numbers are automatically formatted with thousand separators (e.g., 3,600,000 instead of 3600000), making it easier to read and verify your input.

Searchable Unit Selection

The unit dropdown includes a search function. Start typing the unit name or symbol (like "kwh" or "calorie") to quickly find what you need.

Customizable Display

Choose which units appear in your results. Group units by category (metric, calorie, electrical, thermal, etc.) and toggle each one individually.

Precision Control

Select from multiple decimal precision options (2, 4, 6, 8) or use Auto mode. Higher precision is useful for scientific calculations, while lower precision keeps results easy to read.

One-Click Copy

Copy individual results or all results at once. Values are copied in a clean format, ready to paste into documents, spreadsheets, or technical reports.

Unit Reference Guide

Built-in reference panel explains each unit's value and typical usage. Helpful when you encounter unfamiliar units like Therm, Electronvolt, or Tonne of Oil Equivalent.

Works Everywhere

Fully responsive design works on desktop, tablet, and mobile devices. Calculate energy conversions wherever you are—at home, in the lab, or on the job site.

Frequently Asked Questions

What is the difference between a calorie and a Calorie?

A lowercase calorie (cal) is a small calorie—the energy needed to raise 1 gram of water by 1°C. A capital Calorie (Cal) or kilocalorie (kcal) equals 1,000 small calories and is what you see on food nutrition labels.

Important: When food labels say "100 Calories," they actually mean 100 kcal or 100,000 small calories.

How do I convert kWh to Joules?

Enter your kWh value in the converter and look at the Joule (J) result. The conversion is straightforward:

1 kWh = 3,600,000 J = 3.6 MJ

Kilowatt-hours measure electrical energy consumption (commonly used on electricity bills), while Joules are the SI base unit of energy used in scientific calculations.

What is a BTU?

A British Thermal Unit (BTU) is the amount of heat energy needed to raise the temperature of 1 pound of water by 1°F. It's commonly used in the United States for rating air conditioning and heating systems.

Conversion: 1 BTU ≈ 1,055 Joules ≈ 0.293 Watt-hours

For example, a 12,000 BTU air conditioner has a cooling capacity of approximately 3.5 kW.

How do I understand my electricity bill?

Electricity is typically billed in kilowatt-hours (kWh). One kWh represents the energy consumed by a 1,000-watt (1 kW) appliance running for one hour.

Examples:

A 100W light bulb running for 10 hours = 1 kWh
A 2,000W space heater running for 30 minutes = 1 kWh
A 50W laptop running for 20 hours = 1 kWh

Use this converter to translate kWh into other energy units if needed for comparisons or calculations.

What is an electronvolt (eV)?

An electronvolt (eV) is a tiny unit of energy used in particle physics, atomic physics, and chemistry. It equals the energy gained by a single electron when it moves through an electric potential difference of one volt.

Conversion: 1 eV = 1.602 × 10⁻¹⁹ Joules

This unit is particularly useful when dealing with atomic and subatomic particles, where Joules would result in inconveniently small numbers. For example, the ionization energy of a hydrogen atom is about 13.6 eV.

How do calories relate to kilojoules on food labels?

Many countries use kilojoules (kJ) instead of Calories on nutrition labels. The conversion factor is:

1 kcal (Calorie) = 4.184 kJ

So a food item with 100 kcal contains approximately 418 kJ of energy. Some countries display both units on their labels for convenience.

Quick tip: To convert kJ to kcal, divide by 4.184. To convert kcal to kJ, multiply by 4.184.

What is a therm?

A therm is a unit of heat energy equal to 100,000 BTU. It's commonly used for billing natural gas consumption in the United States.

Conversions:

1 therm = 100,000 BTU
1 therm ≈ 105.5 MJ (Megajoules)
1 therm ≈ 29.3 kWh (Kilowatt-hours)

Natural gas bills typically show consumption in therms or CCF (hundred cubic feet), with therms being the energy content measure.

How accurate are the conversions?

The converter uses internationally recognized conversion factors with high precision. For most practical purposes, the results are accurate to many decimal places.

Use the precision selector to display the accuracy level you need:

2 decimals: Suitable for everyday calculations and general use
4-6 decimals: Appropriate for engineering and technical applications
8 decimals: Ideal for scientific research and high-precision requirements
Auto mode: Automatically adjusts precision based on the magnitude of the value

Why are my settings saved?

The converter uses your browser's local storage to remember your preferences, including:

Selected decimal precision
Visible/hidden units
Last used source unit

Privacy note: This data stays entirely on your device and is never sent to any server. Clear your browser data or use incognito mode to reset all settings.