British Thermal Units to Tons Of TNT (BTU to tTNT)

1 British thermal unit equals 2.521644007×10⁻⁷ tons of TNT (rounded).

1 British thermal unit = 2.521644007×10⁻⁷ tons of TNT

How to convert British thermal units to tons of TNT

To convert British thermal units to tons of TNT, multiply the number of British thermal units by 2.521644007×10⁻⁷. The factor is rounded to 10 significant digits. To go the other way, multiply tons of TNT by 3,965,666.831 (rounded).

tons of TNT = British thermal units × 2.521644007×10⁻⁷

Example: 10 British thermal units = 0.000002521644007 tons of TNT.

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)

US & ImperialCurrent unit

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

Ton Of TNT (tTNT)

ScientificCurrent unit

Exactly 4.184 gigajoules by convention (one tonne of TNT). The unit for explosions; a megaton is a million of them.

Explosive yields are quoted against a reference charge, and the ton of TNT is the one that stuck. Real TNT does not release a single fixed amount of energy: measured values run near 4,686 joules per gram, calculations give about 4,853, and a large open blast can burn more of its products in air than a small one. To sidestep the argument, the energy of a gram of TNT was set by convention at 4,184 joules, one kilocalorie, so a ton is exactly 4.184 gigajoules.

That makes a kiloton 4.184 terajoules and a megaton 4.184 petajoules. The scale is mostly used for nuclear weapons and asteroid impacts. The Hiroshima bomb is usually put at about 15 kilotons (63 terajoules) and the Nagasaki bomb at about 20 kilotons (84 terajoules). NIST lists the ton of TNT at 4.184 x 10^9 joules as an exact factor, matching the convention used here.

1 ton of TNT = 4,184,000,000 joules (exactly).

Sources: Wikipedia: TNT equivalent; NIST SP 811, Appendix B.8

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