Convert Megajoule to Calorie (MJ → cal)

Converting megajoules to calories is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in megajoules

   Start with the number of megajoules (MJ) you want to convert.
2. 2
   Multiply by 239,005.74

   The conversion factor from MJ to cal is 239,005.74. Multiply your value by this number.
3. 3
   Read the result in calories

   The result is your value in calories (cal).

Multiply the value in megajoules by 239,005.74. For the reverse direction, multiply by 0.000004184.

• ✓1 MJ = 1000 kJ = 0.278 kWh.
• ✓Natural gas heat content often quoted as MJ/m³.
• ✓For fuel economy, use MJ/km or L/100km interchangeably.

• ✗Confusing MJ with MW (power).
• ✗Using MJ for electricity bills — kWh is standard.
• ✗Mixing fuel energy (MJ) with fuel volume (L) without unit conversion.

What is the Megajoule?

The megajoule equals 1,000,000 joules (or 1,000 kilojoules) and is used for measuring fuel energy content, large-scale electrical work, and industrial heat applications. The energy content of food and fuel is often quoted in MJ: a kilogram of gasoline contains about 46 MJ, natural gas has 38 MJ per cubic meter, and a kilogram of coal yields 24 MJ. Vehicle fuel-economy and energy-efficiency calculations use MJ to compare disparate energy sources. Industrial process heating, boiler outputs, and large machinery energy ratings are commonly given in MJ per cycle or MJ per hour. The megajoule relates to the joule (10⁶ J = 1 MJ), the kilojoule (1,000 kJ = 1 MJ), the kilowatt-hour (1 kWh = 3.6 MJ), and the BTU (1 MJ ≈ 948 BTU). For electricity-grid energy accounting, the equivalent kilowatt-hour or megawatt-hour is more common than MJ.

• Fuel energy content reporting
• Natural gas billing in some countries
• Industrial energy consumption

What is the Calorie?

The calorie equals exactly 4.184 joules (the 'thermochemical calorie') and is the historical unit for heat in chemistry and physics. It was originally defined as the heat needed to raise 1 gram of water by 1°C (a definition that varied slightly with starting temperature, hence multiple 'calories' — 4.184 J was set as the exact thermochemical convention). The calorie is widely used in older physics and chemistry literature for reaction energies, specific heat capacities, and thermodynamic calculations. Note: this 'small calorie' (lowercase c) is 1/1000 of the food Calorie (capital C) used in nutrition. The chemistry calorie relates to the joule (4.184 J = 1 cal), the kilocalorie (1,000 cal = 1 kcal = 1 food Calorie), and the BTU (1 BTU ≈ 252 cal). Modern SI usage in scientific publications has largely replaced the calorie with the joule, but it persists in medical and chemistry contexts.

• Thermodynamics and older physics texts
• Chemistry energy calculations
• Some engineering heat-transfer contexts