A watt-hour is 3,600 joules.
Watt-hours to Femtojoules Converter — Wh to fJ
Convert Watt-hour (Wh) to Femtojoule (fJ) using the exact conversion factor (1 watt-hour = 3.6e+18 femtojoule). See the formula, worked examples, conversion table, and common uses.
Watt-hours to Femtojoules 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.
Femtojoule is 1e-15 joule units.
Result = input x 3600 / 1e-15.
Energy uses the joule as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Watt-hours to Femtojoules
Watt-hour and Femtojoule both measure energy, and the conversion is especially useful for comparing nutrition labels (kilocalories) against scientific energy figures (joules). Watt-hour is most often used for phone, laptop, and power-bank battery capacity ratings.
Formula
femtojoules = watt-hours × 3.6e+18
This factor comes from each unit's defined relationship to the category's base unit: 1 watt-hour equals 3600 base units, and 1 femtojoule equals 1e-15 base units, so dividing one by the other gives the direct watt-hour-to-femtojoule factor of 3.6e+18.
Simple example
1 Wh × 3.6e+18 = 3.6e+18 fJ
1 watt-hour = 3.6e+18 femtojoules.
Real-world example
100 Wh × 3.6e+18 = 3.6e+20 fJ
100 watt-hours = 3.6e+20 femtojoules.
Conversion table
| Watt-hour (Wh) | Femtojoule (fJ) |
|---|---|
| 1 Wh | 3.6e+18 fJ |
| 10 Wh | 3.6e+19 fJ |
| 100 Wh | 3.6e+20 fJ |
| 500 Wh | 1.8e+21 fJ |
| 1,000 Wh | 3.6e+21 fJ |
| 2,000 Wh | 7.2e+21 fJ |
Reverse conversion: Femtojoule to Watt-hour
3.6e+18 fJ × 2.777778e-19 = 1 Wh
3.6e+18 femtojoules = 1 watt-hours.
watt-hours = femtojoules × 2.777778e-19
For a page dedicated to this direction, see Femtojoule to Watt-hour.
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 Femtojoule (fJ)
Femtojoule is 1e-15 joule units.
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).
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many femtojoules are in 1 watt-hour?
1 watt-hour equals 3.6e+18 femtojoules, using the exact defined conversion factor rather than an estimate.
How do I convert watt-hour to femtojoule?
Multiply the watt-hour value by 3.6e+18. The converter above does this instantly to whatever precision you set.
How do I convert femtojoule back to watt-hour?
Use the reverse factor: 1 femtojoule equals 2.777778e-19 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 femtojoule?
Femtojoule (fJ) is a unit of energy.
Is the watt-hour to femtojoule conversion exact?
Yes. Both watt-hour and femtojoule are defined by fixed standards rather than physical artifacts, so the factor of 3.6e+18 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