British Thermal Units to Megajoules (BTU to MJ)
1 British thermal unit equals 0.001055055853 megajoules (rounded).
How to convert British thermal units to megajoules
To convert British thermal units to megajoules, multiply the number of British thermal units by 0.001055055853. The factor is rounded to 10 significant digits. To go the other way, multiply megajoules by 947.8171203 (rounded).
megajoules = British thermal units × 0.001055055853
Example: 10 British thermal units = 0.01055055853 megajoules.
The 'calorie' on food labels is really a kilocalorie. The thermochemical calorie (4.184 J) is used here unless marked IT.
About these units
British Thermal Unit (BTU)
The International Table BTU, exactly 1,055.05585262 joules. The energy to heat one pound of water by one degree Fahrenheit; used for heating, cooling and gas appliances in the US.
Few energy units come in as many versions as the British thermal unit. It was defined as the heat needed to raise one pound of liquid water by one degree Fahrenheit, but because water's heat capacity shifts slightly with temperature, definitions differ by up to 0.5 percent: about 1,054.35 J for the thermochemical Btu, 1,054.80 J at 59 degrees Fahrenheit (used for American natural gas pricing), 1,054.68 J at 60 degrees (mainly Canadian), and 1,059.67 J at 39 degrees. A 1942 note suggests the term apparently arose in the United States and was later adopted in Britain.
The version on this site is the International Table Btu, about 1,055.06 J, which comes from the international steam table conferences that tied heat units to the joule. Joule's own 1850 experiments gave 772.692 foot-pounds of work per Btu, the number that first linked heat to mechanical effort.
Today the Btu survives in natural gas pricing (MMBtu means a million Btu), US building energy reporting, and equipment ratings in Btu per hour. One ton of air-conditioning is 12,000 Btu/h, or 3.52 kW. A single wooden kitchen match burning releases about one Btu.
1 British thermal unit = 1,055.055853 joules (approximately).
Sources: Wikipedia: British thermal unit; Wikipedia: James Prescott Joule
Megajoule (MJ)
One million joules. Used for fuel energy content and natural gas billing in many countries.
Picture a one-tonne car moving at 44.7 m/s, about 100 miles per hour: its kinetic energy is roughly one megajoule. Because the joule was originally conceived in 1882 as 10 million ergs, a megajoule is 10 to the 13th ergs, a figure that shows how little the old CGS unit suited everyday work and why the joule won out.
Food provides a more familiar benchmark. A Snickers bar of 280 food calories holds about 1.2 MJ, and a day's 2,000 food calories for a moderately active woman come to about 8.4 MJ. A kilowatt-hour of electricity is exactly 3.6 MJ, and exploding a kilogram of TNT releases about 4.2 MJ.
In other words the megajoule sits at the scale of a single serving of fuel, food or electricity, which is why it turns up in energy-content tables where joules would give unwieldy numbers.
1 megajoule = 1,000,000 joules (exactly).
Sources: Wikipedia: Joule; Wikipedia: Orders of magnitude (energy); Wikipedia: Kilowatt-hour
Related conversions
- Megajoules to British thermal units (reverse)
- British thermal units to joules
- British thermal units to kilojoules
- British thermal units to watt-hours
- British thermal units to kilowatt-hours
- British thermal units to calories
- British thermal units to kilocalories
- British thermal units to gigajoules
- British thermal units to megawatt-hours
- British thermal units to foot-pounds
- British thermal units to millijoules
- British thermal units to electronvolts
- British thermal units to kiloelectronvolts
- Joules to megajoules
- Kilojoules to megajoules
- Watt-hours to megajoules
- Kilowatt-hours to megajoules
- Calories to megajoules
- Kilocalories to megajoules
- Gigajoules to megajoules
- Megawatt-hours to megajoules
- Foot-pounds to megajoules
See all energy units.