Convert Megajoules to Watt-hours
1 megajoule (MJ) equals 277.7777778 watt-hours (Wh).
1 MJ = 277.7777778 Wh
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk megajoule to watt-hour converter to paste a column from Excel.
How to Convert Megajoule to Watt-hour
- 1 MJ = 277.7777778 Wh
- 1 Wh = 0.0036 MJ
- Example: convert 15 MJ to Wh: 15 MJ = 15 × 277.7777778 Wh = 4166.666667 Wh
Formula
Wh = MJ × 277.7777777778
Derivation from SI units:
- 1 MJ = 10⁶ J
- 1 Wh = 1 W × 3600 s = 3600 J
- 1 MJ = 1000000 J ÷ 3600 J per Wh = 277.7777777778 Wh
Both units are defined exactly, so the factor is exact. Megajoule definition: megajoule; Watt-hour definition: watt-hour.
Worked examples
- A reading of 35 MJ converts to 9722.222222 Wh.
35 MJ × 277.7777778 = 9722.222222 Wh - A value of 50 MJ is 13888.88889 Wh.
50 MJ × 277.7777778 = 13888.88889 Wh
Megajoule to Watt-hour conversion table
| Megajoules (MJ) | Watt-hours (Wh) |
|---|---|
| 1 MJ | 277.7777778 Wh |
| 3.6 MJ | 1000 Wh |
| 10 MJ | 2777.777778 Wh |
| 35 MJ | 9722.222222 Wh |
| 38 MJ | 10555.55556 Wh |
| 45 MJ | 12500 Wh |
| 50 MJ | 13888.88889 Wh |
| 100 MJ | 27777.77778 Wh |
| 1000 MJ | 277777.7778 Wh |
Where it's used
Megajoules are used for fuel heating values (natural gas ≈ 38 MJ/m³, diesel ≈ 45 MJ/kg), while watt-hours appear in battery capacity (phone ≈ 15 Wh; airline limit 100 Wh per power bank). Both measure energy, work and heat, so the conversion is a fixed factor.
Megajoule to other energy units
| Conversion | 1 MJ equals |
|---|---|
| megajoule to joule | 1000000 J |
| megajoule to kilojoule | 1000 kJ |
| megajoule to calorie | 239005.7361 cal |
| megajoule to kilocalorie | 239.0057361 kcal |
| megajoule to watt-hour | 277.7777778 Wh |
| megajoule to kilowatt-hour | 0.2777777778 kWh |
| megajoule to BTU | 947.8171203 BTU |
| megajoule to therm | 0.00948043428 thm |
| megajoule to electronvolt | 6.241509074 × 10²⁴ eV |
| megajoule to foot-pound | 737562.1493 ft·lbf |
| megajoule to erg | 10000000000000 erg |
Frequently asked questions
How many watt-hours are in 1 megajoule?
1 MJ = 277.7777778 Wh.
How do I convert megajoules to watt-hours?
Multiply the value in MJ by 277.7777778. For example, 15 MJ × 277.7777778 = 4166.666667 Wh.
Is the MJ to Wh conversion exact?
Yes. Both units are defined exactly, so the ratio is exact; its decimal form does not terminate and is shown here to 10 significant figures (more with the precision selector).
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 7, SI prefixes.
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "watt hour (W·h)".
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Megajoules to Watt-hours. Retrieved October 17, 2026, from https://scientificconverters.com/energy/megajoules-to-watt-hours/
IEEE
Scientific Converters, "Convert Megajoules to Watt-hours," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/energy/megajoules-to-watt-hours/