megajoules

Megajoule (symbol: MJ) is a unit of energy in the International System of Units (SI). It equals one million joules. The joule is the SI unit of energy or work, defined as the work done when a force of one newton moves an object by one meter. Therefore, 1 MJ = 1,000,000 J = 1,000,000 N·m.

In practical terms, megajoules describe energy at a moderate scale. For context, 1 MJ is about 0.2778 kilowatt-hours, so a 60-watt light bulb running for roughly 4.6 hours consumes about 1 MJ. The energy content of fuels is often expressed in MJ per liter or per kilogram; gasoline is commonly cited around 34–35 MJ per liter.

Megajoules are used across physics, engineering, and energy economics to quantify energy release, storage, or consumption. They sit between kilojoules (kJ) and gigajoules (GJ) on the energy scale, with 1 GJ equal to 1,000 MJ.

Common related concepts include energy density and efficiency calculations. On nutrition labels, energy is usually given in kilojoules or kilocalories, while megajoules appear in engineering specs and industrial energy assessments.