Energy Unit Converter

Supports precise conversion between watt-hours, joules, and their various multiples, including common energy units such as kWh, MWh, kJ, and MJ.

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Tool Usage

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1Settings

2Convert

3Copy Export

Input ValueSupports decimals and scientific notation

Source Unit

Main Result Unit

Quick Input

Common Use Cases

Batch DataOne value per line, unit optional

Use “value unit symbol”. If no unit is given, the default source unit below is used.

Default Source Unit

Target Unit

Display Precision

Number Format

Copy Format

Main result

1 kilowatt-hour = 3,600,000 joules

Select parameters to start converting.

Joule base3,600,000 J

Unit categoryElectrical energy units

Result count20 units

Common references

Copy, formulas & history

Conversion history

Instructions

Software Instructions

Select a conversion mode: Two modes are available at the top:
- One-to-many conversion: Enter one value and display the conversion results for all supported units at once.
- Precise conversion: Select a source unit and a target unit to focus on one-to-one conversion results and formulas.
Enter an energy value: Enter the energy value to be converted in the "Input value" box. Decimals and large values are supported. The system automatically validates the input and provides friendly prompts for negative numbers and overflow values.
Select the input unit: Choose the energy unit corresponding to the input value from the dropdown menu:
- Watt-hour units: milliwatt-hour (mWh), watt-hour (Wh), kilowatt-hour (kWh), megawatt-hour (MWh), gigawatt-hour (GWh)
- Joule units: joule (J), kilojoule (kJ), megajoule (MJ), gigajoule (GJ)
- Calorie units: calorie (cal), kilocalorie/Calorie (kcal)
- Imperial units: British thermal unit (BTU), foot-pound force (ft·lbf)
- Physical units: electronvolt (eV), kiloelectronvolt (keV), megaelectronvolt (MeV), erg (erg)
- Other units: ton of TNT equivalent (tTNT), kilowatt-second (kW·s)
Number format settings: Customize how results are displayed:
- Number format: automatic, standard decimal, scientific notation, engineering notation (exponent is a multiple of 3).
- Decimal places: automatically or manually specify precision from 2 to 10 decimal places.
Quick input: Click preset value buttons (1, 100, 1000, 3600, 1000000) to quickly enter common energy values.
Common scenarios: Click scenario buttons (such as "1 kWh", "1 kcal", "phone battery", "electric vehicle", "1 ton TNT", "1 BTU") to fill in the corresponding value and unit with one click and quickly get conversion results.
View conversion results: The system automatically calculates and displays the energy value in all supported units, with the current input unit highlighted.
View conversion formulas: Click the "View conversion formulas" button to display the conversion coefficients and principles from the source unit to all target units.
Copy results: Click any result item to copy a single value, or click the "Copy all results" button to copy all conversion results.
Reverse input: Double-click any result row to set that result value as the new input value and automatically recalculate, enabling two-way interactive conversion.
Conversion history: The system automatically saves the latest 20 conversion records. Click a history item to quickly restore it, with one-click clearing supported.
Unit comparison table: Click the "Expand" button to view the complete unit conversion coefficient table and understand the conversion relationship between all units and joules.
Dark mode: Supports manual switching between dark/light themes and also automatically detects system preference settings.
Keyboard shortcuts: Press Enter to focus the input box, Esc to clear the input, and Tab to switch unit selection.
Reference information: View the common energy reference table to learn about typical energy consumption for different devices and scenarios.

FAQ

A: Watt-hour (Wh) is a common unit of electrical energy, representing the energy consumed by 1 watt of power over 1 hour; joule (J) is the international standard unit of energy. 1 watt-hour = 3600 joules. Electricity bills are usually calculated in kilowatt-hours (kWh), while joules are more commonly used in physics.

A: A kilowatt-hour (kWh), commonly known as a "unit" of electricity, is the standard billing unit used by power companies. 1 kilowatt-hour represents the electrical energy consumed by a 1000-watt appliance running for 1 hour. For example, a 100-watt light bulb running for 10 hours consumes 1 kilowatt-hour of electricity.

A: 1 calorie (cal) = 4.184 joules (J), and 1 kilocalorie/Calorie (kcal) = 4184 joules. Calories are commonly used on food nutrition labels and in human metabolism calculations. For example, a bowl of rice contains about 230 kcal, equivalent to about 962 kilojoules.

A: The British Thermal Unit (BTU) is an imperial unit of energy, defined as the amount of heat required to raise 1 pound of water by 1 degree Fahrenheit. 1 BTU ≈ 1055.06 joules. It is commonly used in heating, ventilation, and air conditioning (HVAC) systems, natural gas measurement, and other fields, and is widely used in Europe and the United States.

A: The electronvolt (eV) is a unit of energy commonly used in particle physics and quantum mechanics, defined as the kinetic energy gained by an electron passing through an electric potential difference of 1 volt. 1 eV ≈ 1.602×10⁻¹⁹ joules. Because the energies of atoms and subatomic particles are extremely small, expressing them in joules is inconvenient, so units such as eV, keV, and MeV are used.

A: Electricity consumption = power (kW) × usage time (h). For example, if a 2000-watt electric water heater runs for 3 hours, the electricity consumption = 2kW × 3h = 6kWh. Once you know the electricity consumption, you can use this tool to convert it to other energy units such as joules, calories, and BTU.

A: Electric vehicle battery capacity is usually expressed in kWh, such as a 75kWh battery pack. This means the battery can store 75 kilowatt-hours of electrical energy when fully charged, equivalent to 270 million joules. The larger the capacity, the longer the driving range usually is. You can use the "Electric Vehicle" scenario button in this tool to quickly view the conversion results.

A: mAh is a unit of electric charge, while Wh is a unit of energy. Conversion formula: Wh = mAh × voltage (V) ÷ 1000. For example, a 5000mAh, 3.85V phone battery has an energy of 5000×3.85÷1000=19.25Wh. You can click the "Phone Battery" scenario button to quickly view the corresponding conversion values in joules, calories, and more.

A: Ton of TNT equivalent is an energy unit used to measure explosive power. 1 ton of TNT equivalent = 4.184×10⁹ joules = 4.184GJ. It is commonly used to describe the scale of energy released by nuclear weapons, large explosions, or celestial impacts. For example, the Hiroshima atomic bomb was about 15,000 tons of TNT equivalent.

A: When the conversion result is very large (such as converting GWh to electronvolts) or very small, the system displays it in scientific notation by default. You can also manually switch to standard decimal, scientific notation, or engineering notation via the "Number Format" option, and customize the number of decimal places to meet readability needs in different scenarios.

A: In scientific notation, the exponent can be any integer (such as 3.6×10⁶), while in engineering notation, the exponent must be a multiple of 3 (such as 3.6×10⁶ or 360×10³). This makes it easier to match SI prefixes (kilo, mega, giga, etc.) and is more practical in engineering fields.

A: The tool uses standard physical conversion formulas and performs precise calculations based on joules. All conversion factors use internationally recognized values (such as 1 eV = 1.602176634×10⁻¹⁹ J). Custom decimal places are supported (up to 10), meeting the accuracy requirements of engineering calculations and scientific research.

A: Conversion history is saved in the browser's local storage (localStorage), with up to 20 records retained. The data is stored only on your device and will not be uploaded to the server. You can delete it by clearing browser data or clicking the "Clear History" button.

A: Solar power generation = installed capacity (kW) × effective sunlight hours (h) × system efficiency. For example, for a 5 kW home photovoltaic system with 5 hours of sunlight and 80% efficiency, the daily power generation is approximately 5×5×0.8=20 kWh. You can use this tool to convert it into joules, kilocalories, BTU, and other energy units for comparison.

Energy Unit Converter

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Tool Usage

Instructions

Software Instructions

FAQ

Q: What is the difference between watt-hours and joules?

Q: What does kilowatt-hour mean?

Q: How do you convert calories and joules?

Q: What is a British Thermal Unit (BTU)?

Q: In what scenarios is the electronvolt (eV) used?

Q: How do you calculate the electricity consumption of an appliance?

Q: How should electric vehicle battery capacity be understood?

Q: What is the relationship between phone battery capacity in mAh and Wh?

Q: What does ton of TNT equivalent mean?

Q: Why are some results displayed in scientific notation?

Q: What is the difference between engineering notation and scientific notation?

Q: How is conversion accuracy ensured?

Q: Where is the conversion history saved?

Q: How is solar power generation calculated?

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