Electronvolts to British Thermal Units (eV to BTU)
1 electronvolt equals 1.518570443×10⁻²² British thermal units (rounded).
How to convert electronvolts to British thermal units
To convert electronvolts to British thermal units, multiply the number of electronvolts by 1.518570443×10⁻²². The factor is rounded to 10 significant digits. To go the other way, multiply British thermal units by 6.585140678×10²¹ (rounded).
British thermal units = electronvolts × 1.518570443×10⁻²²
Example: 10 electronvolts = 1.518570443×10⁻²¹ British thermal units.
The 'calorie' on food labels is really a kilocalorie. The thermochemical calorie (4.184 J) is used here unless marked IT.
About these units
Electronvolt (eV)
Exactly 1.602176634×10⁻¹⁹ joules, the energy gained by an electron moving through one volt. Used in atomic and particle physics.
Particle physicists adopted this unit because a charged particle crossing a voltage V gains energy qV, so an electron accelerated through one volt in a vacuum gains exactly one electronvolt. Since the 2019 revision of the SI, the elementary charge is fixed, which makes 1 eV exactly 1.602176634 x 10^-19 J. The NIST appendix page still shows a rounded, non-exact value, reflecting the time before this redefinition. The unit is not part of the SI itself.
It suits the atomic world. Visible photons carry roughly 1.65 to 3.26 eV, green light at 532 nm is about 2.33 eV, and ionising hydrogen needs 13.6 eV. Molecular bonds are on the order of 1 to 10 eV each, and thermal motion at 20 degrees Celsius corresponds to about 0.025 eV. Particle masses are also quoted in eV/c squared, so the proton is about 938 million of them. Larger multiples such as keV, MeV and GeV extend the scale upward.
1 electronvolt = 1.602176634×10⁻¹⁹ joules (exactly).
Sources: Wikipedia: Electronvolt; NIST SP 811, Appendix B.8 (energy conversion factors)
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
Related conversions
- British thermal units to electronvolts (reverse)
- Electronvolts to joules
- Electronvolts to kilojoules
- Electronvolts to watt-hours
- Electronvolts to kilowatt-hours
- Electronvolts to calories
- Electronvolts to kilocalories
- Joules to British thermal units
- Kilojoules to British thermal units
- Watt-hours to British thermal units
- Kilowatt-hours to British thermal units
- Calories to British thermal units
- Kilocalories to British thermal units
- Megajoules to British thermal units
- Gigajoules to British thermal units
- Megawatt-hours to British thermal units
- Foot-pounds to British thermal units
- Millijoules to British thermal units
- Kiloelectronvolts to British thermal units
See all energy units.