A watt-hour is 3,600 joules.
Watt-hours to Joules Converter — Wh to J
Convert Watt-hour (Wh) to Joule (J) using the exact conversion factor (1 watt-hour = 3,600 joule). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Watt-hours to Joules converter
Converter
Energy Converter
Convert joules, calories, kilowatt-hours, BTU, electronvolts, therms, and mechanical work units.
Context values
Some unit families need one extra value for a physically accurate result.
The joule is the SI derived unit of energy.
Result = input x 3600 / 1.
Energy uses the joule as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Watt-hours to Joules
Watt-hour and Joule both measure energy, and the conversion is especially useful for comparing nutrition labels (kilocalories) against scientific energy figures (joules). Watt-hour is typically associated with universal — standard consumer-electronics and battery energy unit worldwide, while Joule is typically associated with standard scientific and engineering energy unit worldwide.
Formula
joules = watt-hours × 3600
This factor comes from each unit's defined relationship to the category's base unit: 1 watt-hour equals 3600 base units, and 1 joule equals 1 base unit, so dividing one by the other gives the direct watt-hour-to-joule factor of 3600.
Simple example
1 Wh × 3600 = 3,600 J
1 watt-hour = 3,600 joules.
Real-world example
100 Wh × 3600 = 360,000 J
100 watt-hours = 360,000 joules.
Conversion table
| Watt-hour (Wh) | Joule (J) |
|---|---|
| 1 Wh | 3,600 J |
| 10 Wh | 36,000 J |
| 100 Wh | 360,000 J |
| 500 Wh | 1,800,000 J |
| 1,000 Wh | 3,600,000 J |
| 2,000 Wh | 7,200,000 J |
Reverse conversion: Joule to Watt-hour
1 J × 0.0002777777778 = 0.0002777778 Wh
1 joule = 0.0002777778 watt-hours.
watt-hours = joules × 0.000277777777778
For a page dedicated to this direction, see Joule to Watt-hour.
Watt-hour vs. Joule
| Aspect | Watt-hour | Joule |
|---|---|---|
| Family | metric derived energy unit | SI derived unit |
| Typical use | Phone, laptop, and power-bank battery capacity ratings | Physics and engineering energy calculations |
| Where it's used | Universal — standard consumer-electronics and battery energy unit worldwide | Standard scientific and engineering energy unit worldwide |
Understanding the Watt-hour
Watt-hour (Wh) measures energy. The energy delivered by one watt of power sustained for one hour — equal to 3,600 joules. It is classified as a metric derived energy unit.
Where it's used: Universal — standard consumer-electronics and battery energy unit worldwide
Wh vs. kWh. The same unit at different scales: 1,000 Wh equals 1 kWh. Wh suits small consumer-electronics batteries; kWh is used for household electricity billing and larger energy storage.
Uses of the Watt-hour today
- Phone, laptop, and power-bank battery capacity ratings
- Electric-vehicle battery capacity specifications
- Small-scale renewable energy (solar panel) output ratings
Understanding the Joule
Joule (J) measures energy. The joule is the SI derived unit of energy, defined as the work done by one newton acting over one meter. It is classified as a SI derived unit.
Where it's used: Standard scientific and engineering energy unit worldwide
Uses of the Joule today
- Physics and engineering energy calculations
- Electrical energy in scientific contexts (though kWh is used for billing)
- Nutrition labeling in some countries (alongside or instead of calories)
History of the Joule
The joule is named after English physicist James Prescott Joule, whose experiments in the 1840s established the mechanical equivalent of heat — demonstrating that mechanical work and heat are interchangeable forms of energy, foundational to the first law of thermodynamics.
The unit itself was formally adopted as the SI derived unit of energy by international agreement as part of the broader SI system, defined coherently from the base units (kg, m, s) rather than as an independent physical standard.
Historical origin. Joule was not the invention of a single named person; it developed through the process described above.
Watt-hour — sources
- BIPM SI Brochure — Watt-hour as a common energy unit derived from the coherent SI units watt and second (via the hour).
Joule — sources
- BIPM SI Brochure — Coherent derived units — Defines the joule as the SI unit of energy.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many joules are in 1 watt-hour?
1 watt-hour equals 3,600 joules, using the exact defined conversion factor rather than an estimate.
How do I convert watt-hour to joule?
Multiply the watt-hour value by 3600. The converter above does this instantly to whatever precision you set.
How do I convert joule back to watt-hour?
Use the reverse factor: 1 joule equals 0.0002777778 watt-hours. You can also use the swap control in the converter above to flip the direction instantly.
What is a watt-hour?
Watt-hour (Wh) measures energy. The energy delivered by one watt of power sustained for one hour — equal to 3,600 joules. It is classified as a metric derived energy unit.
What is a joule?
Joule (J) measures energy. The joule is the SI derived unit of energy, defined as the work done by one newton acting over one meter. It is classified as a SI derived unit.
Is the watt-hour to joule conversion exact?
Yes. Both watt-hour and joule are defined by fixed standards rather than physical artifacts, so the factor of 3600 used above is exact to as many digits as you choose to display.
What is the difference between wh vs. kwh?
The same unit at different scales: 1,000 Wh equals 1 kWh. Wh suits small consumer-electronics batteries; kWh is used for household electricity billing and larger energy storage.
Where is the watt-hour still used today?
Universal — standard consumer-electronics and battery energy unit worldwide