Convert Watt-hours to Megajoules
1 watt-hour (Wh) equals 0.0036 megajoules (MJ).
1 Wh = 0.0036 MJ
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk watt-hour to megajoule converter to paste a column from Excel.
How to Convert Watt-hour to Megajoule
- 1 Wh = 0.0036 MJ
- 1 MJ = 277.7777778 Wh
- Example: convert 15 Wh to MJ: 15 Wh = 15 × 0.0036 MJ = 0.054 MJ
Formula
MJ = Wh × 0.0036
or MJ = Wh ÷ 277.7777777778
Derivation from SI units:
- 1 Wh = 1 W × 3600 s = 3600 J
- 1 MJ = 10⁶ J
- 1 Wh = 3600 J ÷ 1000000 J per MJ = 0.0036 MJ
Both units are defined exactly, so the factor is exact. Watt-hour definition: watt-hour; Megajoule definition: megajoule.
Worked examples
- A reading of 20 Wh converts to 0.072 MJ.
20 Wh × 0.0036 = 0.072 MJ - A value of 100 Wh is 0.36 MJ.
100 Wh × 0.0036 = 0.36 MJ
Watt-hour to Megajoule conversion table
| Watt-hours (Wh) | Megajoules (MJ) |
|---|---|
| 1 Wh | 0.0036 MJ |
| 5 Wh | 0.018 MJ |
| 10 Wh | 0.036 MJ |
| 15 Wh | 0.054 MJ |
| 20 Wh | 0.072 MJ |
| 50 Wh | 0.18 MJ |
| 60 Wh | 0.216 MJ |
| 75 Wh | 0.27 MJ |
| 100 Wh | 0.36 MJ |
| 160 Wh | 0.576 MJ |
| 500 Wh | 1.8 MJ |
| 1000 Wh | 3.6 MJ |
Where it's used
Watt-hours are used for battery capacity (phone ≈ 15 Wh; airline limit 100 Wh per power bank), while megajoules appear in fuel heating values (natural gas ≈ 38 MJ/m³, diesel ≈ 45 MJ/kg). Both measure energy, work and heat, so the conversion is a fixed factor.
Watt-hour to other energy units
| Conversion | 1 Wh equals |
|---|---|
| watt-hour to joule | 3600 J |
| watt-hour to kilojoule | 3.6 kJ |
| watt-hour to megajoule | 0.0036 MJ |
| watt-hour to calorie | 860.4206501 cal |
| watt-hour to kilocalorie | 0.8604206501 kcal |
| watt-hour to kilowatt-hour | 0.001 kWh |
| watt-hour to BTU | 3.412141633 BTU |
| watt-hour to therm | 0.00003412956341 thm |
| watt-hour to electronvolt | 2.246943267 × 10²² eV |
| watt-hour to foot-pound | 2655.223737 ft·lbf |
| watt-hour to erg | 36000000000 erg |
Frequently asked questions
How many megajoules are in 1 watt-hour?
1 Wh = 0.0036 MJ.
How do I convert watt-hours to megajoules?
Multiply the value in Wh by 0.0036, or divide it by 277.7777778. For example, 15 Wh × 0.0036 = 0.054 MJ.
Is the Wh to MJ conversion exact?
Yes. Both units are defined exactly, and 1 Wh is exactly 0.0036 MJ.
Sources
- 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)".
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 7, SI prefixes.
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 Watt-hours to Megajoules. Retrieved October 17, 2026, from https://scientificconverters.com/energy/watt-hours-to-megajoules/
IEEE
Scientific Converters, "Convert Watt-hours to Megajoules," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/energy/watt-hours-to-megajoules/