Joules to Watt-hours
Convert joules to watt-hours instantly. 1 J = 0.0002777778 Wh. Includes the exact factor, a conversion table of common values and the definition of both units.
How to convert joules to watt-hours
To convert joules to watt-hours, divide by 3,600 (multiply by 0.0002777778). The relationship is fixed, so the same factor works for any quantity — there is nothing to look up and nothing that changes with temperature, location or context.
Wh = J × 0.0002777778
Joules to Watt-hours conversion table
The values people look up most often, rounded for reading. Use the calculator above for anything in between.
| Joules | Watt-hours |
|---|---|
| 1 J | 0.0002778 Wh |
| 2 J | 0.0005556 Wh |
| 3 J | 0.0008333 Wh |
| 5 J | 0.001389 Wh |
| 10 J | 0.002778 Wh |
| 20 J | 0.005556 Wh |
| 25 J | 0.006944 Wh |
| 50 J | 0.013889 Wh |
| 100 J | 0.027778 Wh |
| 500 J | 0.138889 Wh |
| 1,000 J | 0.277778 Wh |
What is a joule?
The SI unit of energy: one newton-metre, or one watt for one second.
What is a watt-hour?
One watt sustained for one hour. Battery capacity is quoted this way.
The formula
Wh = J × 0.0002777778
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the Joules to Watt-hours
- Type the number of joules you want to convert.
- Read the result in watt-hours straight away — there is no button to press.
- Check the table below for the values that come up most often, or reverse the conversion with the linked watt-hours to joules page.
Joules to Watt-hours — frequently asked questions
How many watt-hours are in a joule?
One joule equals 0.0002777778 Wh. Wh = J × 0.0002777778
What is the formula to convert joules to watt-hours?
The formula is Wh = J × 0.0002777778. It is an exact definition rather than an approximation, so the conversion never drifts no matter how large the number.
How do I convert watt-hours back to joules?
Divide instead of multiplying: one watt-hour is 3,600 J. The reverse converter is linked in the related tools list.
Is this conversion exact?
Yes. Both units are defined against the same base unit by international agreement, so the factor is exact — any rounding you see is only in the display, which you can widen by entering more decimal places.
Is this joules to watt-hours free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
What people search for
This page answers each of these searches. They are the exact phrases visitors use to find the joules to watt-hours.
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed August 19, 2026 · Calculation runs client-side · No data collected · Report an error