megajoule (MJ)
1 megajoule = 1,000,000 joules
What is megajoule?
A megajoule is a unit of energy equal to one million joules. It is used in industrial energy calculations, explosive yield estimations, and large-scale thermodynamic systems.
Notes: Metric unit
Real-world uses
Megajoules are used in energy analysis for fuel content (1 litre of petrol contains about 34.2 MJ), building energy ratings, and industrial process energy requirements. Life cycle assessment (LCA) studies report embodied energy in MJ per unit of material.
History
The megajoule became a standard unit in energy engineering and policy analysis during the 20th century. It provides a convenient scale for comparing fuel energy content, industrial processes, and building energy performance across different energy sources.
Common mistakes
Confusing MJ with MWh—1 MWh = 3,600 MJ. Also, when comparing fuel energy densities, failing to distinguish between lower heating value (LHV) and higher heating value (HHV), which can differ by 5–10% for hydrocarbon fuels.
When is this conversion used?
Electricity bills use kilowatt-hours while physics calculations use joules. Converting between them is essential for energy audits, comparing appliance efficiency, and understanding power consumption.
How to convert megajoule to joule
To convert megajoule to joule, multiply the value by 1,000,000.
Conversion formula (from base unit)
x * 1e6
Measurement standards
The joule is the SI derived unit of energy, defined as one kilogram-metre-squared per second-squared (kg·m²/s²). The kilowatt-hour, equal to exactly 3.6 megajoules, is accepted for use with the SI by the BIPM for practical electricity metering.
Did you know?
A single bolt of lightning releases roughly 1 to 5 gigajoules of energy, yet only a small fraction reaches the ground as electrical current. Most of the energy dissipates as light, heat, and the thunder shockwave.
| megajoules | joules |
|---|---|
| 0.1 | 100,000 |
| 0.5 | 500,000 |
| 1 | 1,000,000 |
| 2 | 2,000,000 |
| 5 | 5,000,000 |
| 10 | 10,000,000 |
| 25 | 25,000,000 |
| 50 | 50,000,000 |
| 100 | 100,000,000 |
| 250 | 250,000,000 |
| 500 | 500,000,000 |
| 1,000 | 1.000000e+09 |
Common values
| megajoules | joules | |
|---|---|---|
| A food calorie (1 kcal) | 0.004184 megajoules | 4,184 joules |
| A AA battery | 0.00936 megajoules | 9,360 joules |
| Boiling a kettle | 0.42 megajoules | 420,000 joules |
| Daily human diet (2000 kcal) | 8.368 megajoules | 8,368,000 joules |
| 1 gallon of gasoline | 131.76 megajoules | 131,760,000 joules |
Full megajoule conversion table
| Unit | Value | Factor |
|---|---|---|
| joule | 1 MJ = 1,000,000 J | × 1,000,000 |
| kilojoule | 1 MJ = 1,000 kJ | × 1,000 |
| kilowatt hour | 1 MJ = 0.27777778 kWh | × 0.27777778 |
| calorie (thermochemical) | 1 MJ = 239,005.73613767 cal | × 239,005.73613767 |
| kilocalorie (dietary) | 1 MJ = 239.00573614 kcal | × 239.00573614 |
| watt hour | 1 MJ = 277.77777778 Wh | × 277.77777778 |
| electronvolt | 1 MJ = 6.241509e+24 eV | × 6.241509e+24 |
| British thermal unit | 1 MJ = 947.81712031 BTU | × 947.81712031 |
| therm (US) | 1 MJ = 0.00948043 therm | × 0.00948043 |