Watt Hours to Joules
Convert watt hours to joules instantly — one watt-hour is 3600 joules.
| Watt Hours | Joules |
|---|---|
| 1 Wh | 3600 J |
| 2 Wh | 7200 J |
| 3 Wh | 10800 J |
| 5 Wh | 18000 J |
| 10 Wh | 36000 J |
| 25 Wh | 90000 J |
| 50 Wh | 180000 J |
| 100 Wh | 360000 J |
How to use
- Enter a value in the Watt Hours field.
- The Joules figure appears immediately — no button to press.
- Typing in the Joules field converts back to Watt Hours the same way.
- Use the reference table for the values that come up most often.
Watt Hours to Joules formula
Converting watt hours to joules is a single multiplication by 3600.
J = Wh × 3600
Put another way, one watt-hour is exactly 3,600 joules.
Why this factor: the watt-hour and the joule are both defined against the joule, so dividing one definition by the other gives 3600 directly. Both definitions are set out in full below.
To go the other way, divide by 3600 — or use the Joules to Watt Hours converter, which is the same calculation reversed.
Worked example
Given 500 Wh, multiplying by 3600 yields 1800000 J.
500 Wh × 3600 = 1800000 J
The converter above does this for any value you type, in either direction.
What is a watt-hour?
A watt-hour is the energy delivered by one watt of power sustained for one hour.
Definition: Exactly 3,600 joules.
Where it is used: Battery capacity for laptops, e-bikes and power tools, and small-scale energy metering.
Worth knowing: Airline lithium-battery limits are set in watt-hours, which is why laptop and power-bank capacities are labelled in Wh.
What is a joule?
The joule is the SI unit of energy — the work done by one newton acting over one meter.
Definition: Defined as 1 N·m, equivalently one watt-second. Named after James Prescott Joule.
Where it is used: All scientific energy calculations, food energy on European labels, and mechanical work.
Watt Hours vs Joules
The watt-hour is a specialized unit while the joule is an SI unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many joules are in a watt-hour?
One watt-hour equals 3600 joules.
What is the formula to convert watt hours to joules?
Multiply the number of watt hours by 3600. To reverse it, divide by 3600 instead.
How do I convert joules back to watt hours?
Divide by 3600, which is the same as multiplying by 0.000277777778.
How many joules are in 10 watt hours?
10 Wh works out to 36000 J.
Is there anything to watch out for with watt hours?
Airline lithium-battery limits are set in watt-hours, which is why laptop and power-bank capacities are labelled in Wh.
How is the watt-hour defined?
Exactly 3,600 joules.