Authoritative definitions of the International System of Units and SI prefixes.
Dedicated unit pair
Watt-hours to Megajoules
Convert Wh to MJ instantly, then review the formula, assumptions, and rounding guidance.
Energy, work, heat & powerInstant result
Decimals
Formula result = input × 3600 ÷ 1000000. 1 Wh = 0.0036 MJ
Common examples
One value, several units
Joules3,600 J
Kilojoules3.6 kJ
Megajoules0.0036 MJ
Kilowatt-hours0.001 kWh
Thermochemical calories860.4207 cal
Kilocalories0.8604 kcal
BTU (International Table)3.4121 BTU
Conversion table
| Wh | MJ |
|---|---|
| 1 Wh | 0.0036 MJ |
| 2 Wh | 0.0072 MJ |
| 5 Wh | 0.018 MJ |
| 10 Wh | 0.036 MJ |
| 25 Wh | 0.09 MJ |
| 50 Wh | 0.18 MJ |
| 100 Wh | 0.36 MJ |
Conversion chart
1 Wh0.0036 MJ
5 Wh0.018 MJ
10 Wh0.036 MJ
25 Wh0.09 MJ
50 Wh0.18 MJ
Worked example
1 kilowatt-hour equals exactly 3.6 megajoules.
Unit definition
Watt-hours (Wh) One watt-hours equals 3,600 joule.
Unit history
Watt-hours is represented here using its modern SI definition or an internationally accepted relationship to an SI base unit.
Step by step
1. Parse the value, including fractions.
2. Convert Wh to joule.
3. Convert the base value to MJ and apply your display precision.
Understand the result before using it
Watt-hours to Megajoules converts a value measured in Watt-hours (Wh) into the equivalent value in Megajoules (MJ). The numerical value changes because the size and definition of the selected unit changes; the underlying quantity does not.
Calculated result
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.
Formula, assumptions, and example
Formula
result = input × 3600 ÷ 1000000
Assumptions
- Watt-hours and Megajoules represent the same energy, work & heat quantity.
- The input is expressed in Wh; the output is expressed in MJ.
- The unit definitions and conventional relationship shown on this page apply.
Worked example
1 Wh = 0.0036 MJ. For another value, apply the same relationship and round only to the precision your source measurement supports.
When to use it
Good uses
- Read a Wh measurement in a document that expects MJ.
- Compare a watt-hours value with a value reported in megajoules.
- Check the Wh-to-MJ arithmetic before copying the result into another calculation.
Limitations
Common mistakes to avoid
- Do not confuse Wh with another unit that has a similar name or symbol.
- Round the output to a precision justified by the original measurement.
- Verify safety-critical, regulated, laboratory, and contractual conversions against the controlling standard.
Sources and further reading
These references explain the underlying standards or provide authoritative context. Your own contract, institution, clinician, product documentation, local code, or governing standard may be the controlling source.
Guidance on unit names, symbols, conversions, and numerical presentation.
Questions about this calculation
How do I convert Watt-hours to Megajoules?
result = input × 3600 ÷ 1000000 Using the displayed relationship, 1 Wh equals 0.0036 MJ.
How many Megajoules are in one Watt-hours?
One Watt-hours is 0.0036 Megajoules. The displayed digits may be rounded.
Can I reverse the Wh to MJ conversion?
Yes. Swap the source and target units in the converter. The reverse relationship converts MJ back to Wh.
Is the Watt-hours to Megajoules result exact?
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.