Joules to Watt Hours
The joule is the SI unit of energy, defined as the work done by one newton over one meter. A watt-hour is the energy used by a one-watt device running for one hour, used to rate small batteries. 1 J equals ≈0.000277778 Wh, so converting between them is a matter of multiplying by that fixed factor — type any value into the converter below and both sides update instantly as you type.
Both units belong to energy, measured here against energy's base unit (J) — every other energy unit on this site converts through that same reference point, which is why the table below can also be read as a quick cross-check against nearby values.
Formula
Wh = J × ≈0.000277778
J = Wh × 3,600
Worked example: 5 J × ≈0.000277778 = ≈0.00138889 Wh.
Conversion table
| Joule (J) | Watt-hour (Wh) |
|---|---|
| 1 J | ≈0.000277778 Wh |
| 2 J | ≈0.000555556 Wh |
| 3 J | ≈0.000833333 Wh |
| 5 J | ≈0.00138889 Wh |
| 10 J | ≈0.00277778 Wh |
| 20 J | ≈0.00555556 Wh |
| 25 J | ≈0.00694444 Wh |
| 50 J | ≈0.0138889 Wh |
| 100 J | ≈0.0277778 Wh |
| 250 J | ≈0.0694444 Wh |
| 500 J | ≈0.138889 Wh |
| 1,000 J | ≈0.277778 Wh |
Frequently asked
- How many Watt-hours in a joule?
- 1 J equals ≈0.000277778 Wh.
- How do I convert Joules to Watt-hours?
- Multiply the value in J by ≈0.000277778 to get Wh. The converter above does this instantly as you type.
- Is the conversion exact?
- Yes — Joule and Watt-hour are both defined by a fixed conversion factor to energy's base unit (J), so the result shown is exact to the precision displayed, not an approximation.