Tesla (unit)

tesla
tesla
Unit system	SI
Unit of	magnetic flux density
Symbol	T
Named after	Nikola Tesla
In SI base units
1 T	= 1 kg⋅s−2⋅A−1
In Gaussian units
1 T	corresponds to 104 G

The tesla (symbol: T) is the unit of magnetic flux density (B) (also called magnetic B-field) in the International System of Units (SI).

One tesla is equal to one weber per square metre. The unit was announced during the General Conference on Weights and Measures in 1960 and is named in honour of Serbian-American electrical and mechanical engineer Nikola Tesla, upon the proposal of the Slovenian electrical engineer France Avčin. As with every SI unit named after a person, its symbol is upper case (T) but the name of the unit is written in sentence case (tesla).

Definition

A particle, carrying a charge of one coulomb (C), and moving perpendicularly through a magnetic field of one tesla, at a speed of one metre per second (m/s), experiences a force with magnitude one newton (N), according to the Lorentz force law. That is, $T = \frac{N \cdot s}{C \cdot m} .$ Expressed in SI base units, 1 tesla is: $T = \frac{k g}{A \cdot s^{2}},$ where A is ampere, kg is kilogram, and s is second.

In terms of other SI derived units

As an SI derived unit, the tesla can also be expressed in terms of other units. For example, a magnetic flux of 1 weber (Wb) through a surface of one square meter is equal to a magnetic flux density of 1 tesla. That is,

$T = \frac{W b}{m^{2}} .$

Additional equivalences result from the derivation of coulombs from amperes (A), $C = A \cdot s$ : $T = \frac{N}{A \cdot m},$ the relationship between newtons and joules (J), $J = N \cdot m$ : $T = \frac{J}{A \cdot m^{2}},$ and the derivation of the weber from volts (V), $W b = V \cdot s$ : $T = \frac{V \cdot s}{m^{2}} .$

Conversion to non-SI units

The CGS system has a unit similar to the tesla called the gauss. One tesla corresponds to 10⁴ G, but there are subtle differences in the meaning of the units and the gauss is not acceptable for use with SI units according to NIST guidelines.

The unit γ (gamma), formerly used in geophysics and defined as 10^-5 G, corresponds to 10^-9 T. The modern convention is to use the nanotesla (nT) instead of γ.

The 2019 revision of the SI changed the definition of the ampere and that changed the definition of the tesla by 106.67 parts in 10⁹. The revision also changed the definition of the permeability constant, $μ_{0}$ , altering the meaning of conversions between SI units like the tesla and CGS units like the gauss, and making them a little uncertain. Use of these conversions has been discouraged in scholarly journals.

Examples

The following examples are listed in the ascending order of the magnetic-field strength.

25000–65000 nT – the magnitude of Earth's magnetic field at its surface
4×10⁻⁵ T (40 μT) – walking under a high-voltage power line
5×10⁻³ T (5 mT) – the strength of a typical refrigerator magnet
0.3 T – the strength of solar sunspots
1 T to 2.4 T – coil gap of a typical loudspeaker magnet
1.5 T to 3 T – strength of medical magnetic resonance imaging systems in practice, experimentally up to 17 T
4 T – strength of the superconducting magnet built around the CMS detector at CERN
5.16 T – the strength of a specially designed room temperature Halbach array
8 T – the strength of LHC magnets
11.75 T – the strength of INUMAC magnets, largest MRI scanner
13 T – strength of the superconducting ITER magnet system
14.5 T – highest magnetic field strength ever recorded for an accelerator steering magnet at Fermilab
16 T – magnetic field strength required to levitate a frog (by diamagnetic levitation of the water in its body tissues) according to the 2000 Ig Nobel Prize in Physics
17.6 T – strongest field trapped in a superconductor in a lab as of July 2014
20 T – strength of the large scale high temperature superconducting magnet developed by MIT and Commonwealth Fusion Systems to be used in fusion reactors
27 T – maximal field strengths of superconducting electromagnets at cryogenic temperatures
35.4 T – the current (2009) world record for a superconducting electromagnet in a background magnetic field
45 T – the current (2015) world record for continuous field magnets
97.4 T – strongest magnetic field produced by a "non-destructive" magnet
100 T – approximate magnetic field strength of a typical white dwarf star
1200 T – the field, lasting for about 100 microseconds, formed using the electromagnetic flux-compression technique
10⁹ T – Schwinger limit above which the electromagnetic field itself is expected to become nonlinear
10⁸ – 10¹¹ T (100 MT – 100 GT) – magnetic strength range of magnetar neutron stars

Notes and references

1 2 "NIST Guide to the SI, Chapter 5: Units Outside the SI". NIST. January 28, 2016.
↑ "Details of SI units". sizes.com. 2011-07-01. Retrieved 2011-10-04.
1 2 The International System of Units (PDF), V4.01 (9th ed.), International Bureau of Weights and Measures, Jun 2026, ISBN 978-92-822-2272-0
↑ A Dictionary of Earth Sciences (3 ed.). Oxford University Press. January 1, 2008. doi:10.1093/acref/9780199211944.001.0001. ISBN 978-0-19-921194-4."gamma". www.oxfordreference.com. Oxford, UK: Oxford University Press. Retrieved 2026-06-07.
↑ McGraw Hill Encyclopaedia of Physics (2nd edition), C. B. Parker, 1994, ISBN 0-07-051400-3.^{[page needed]}
↑ "SI base unit: ampere (A)". www.bipm.org. Sevres, France: Bureau International des Poids et Mesures. 2019. Retrieved 2026-06-07."Historical perspective: Unit of electric current, ampere". www.bipm.org. Sevres, France: Bureau International des Poids et Mesures. 2019. Retrieved 2026-06-07.
↑ Shisong Li; Qing Wang; Wei Zhao; Songling Huang (2020-07-20). "From μ₀ to e: A Survey of Major Impacts for Electrical Measurements in Recent SI Revision". ieeexplore.ieee.org. IEEE. Retrieved 2026-06-10.
↑ "Ronald B. Goldfarb" (2017). "The Permeability of Vacuum and the Revised International System of Units". ieeexplore.ieee.org. IEEE. Retrieved 2026-06-10.
↑ Finlay, C. C.; Maus, S.; Beggan, C. D.; Bondar, T. N.; Chambodut, A.; Chernova, T. A.; Chulliat, A.; Golovkov, V. P.; Hamilton, B.; Hamoudi, M.; Holme, R.; Hulot, G.; Kuang, W.; Langlais, B.; Lesur, V.; Lowes, F. J.; Lühr, H.; Macmillan, S.; Mandea, M.; McLean, S.; Manoj, C.; Menvielle, M.; Michaelis, I.; Olsen, N.; Rauberg, J.; Rother, M.; Sabaka, T. J.; Tangborn, A.; Tøffner-Clausen, L.; Thébault, E.; Thomson, A. W. P.; Wardinski, I.; Wei, Z.; Zvereva, T. I. (December 2010). "International Geomagnetic Reference Field: the eleventh generation". Geophysical Journal International. 183 (3): 1216–1230. Bibcode:2010GeoJI.183.1216F. doi:10.1111/j.1365-246X.2010.04804.x. hdl:20.500.11850/27303.
↑ "EMF: 7. Extremely low frequency fields like those from power lines and household appliances". ec.europa.eu. Archived from the original on 2021-02-24. Retrieved 2022-05-13.
↑ "Ultra-High Field". Bruker BioSpin. Retrieved 4 October 2011.{{cite web}}: CS1 maint: deprecated archival service (link)
↑ "Superconducting Magnet in CMS". Retrieved 9 February 2013.
↑ "The Strongest Permanent Dipole Magnet" (PDF). Retrieved 2 May 2020.
↑ "ISEULT – INUMAC". Retrieved 17 February 2014.
↑ "ITER – the way to new energy". Retrieved 19 April 2012.
↑ Hesla, Leah (13 July 2020). "Fermilab achieves 14.5-tesla field for accelerator magnet, setting new world record". Retrieved 13 July 2020.
↑ Berry, M. V.; Geim, A. K. (1997). "Of Flying Frogs and Levitrons" by M. V. Berry and A. K. Geim, European Journal of Physics, v. 18, 1997, p. 307–13" (PDF). European Journal of Physics. 18 (4): 307–313. doi:10.1088/0143-0807/18/4/012. S2CID 1499061. Archived from the original (PDF) on 8 October 2020. Retrieved 4 October 2020.
↑ "The 2000 Ig Nobel Prize Winners". August 2006. Retrieved 12 May 2013.)
↑ "Superconductor Traps The Strongest Magnetic Field Yet". 2 July 2014. Retrieved 2 July 2014.
↑ Hartwig, Zachary S. (March 2024). "The SPARC Toroidal Field Model Coil Program". IEEE Transactions on Applied Superconductivity. 34 (2): 1–16. arXiv:2308.12301. doi:10.1109/TASC.2023.3332613. ISSN 1051-8223.
1 2 "Mag Lab World Records". Media Center. National High Magnetic Field Laboratory, USA. 2008. Retrieved 24 October 2015.
↑ "World record pulsed magnetic field". Physics World. 31 August 2011. Retrieved 26 January 2022.)
↑ D. Nakamura, A. Ikeda, H. Sawabe, Y. H. Matsuda, and S. Takeyama (2018), Magnetic field milestone

External links

Gauss ↔ Tesla Conversion Tool

[NIST-SI-1] 1 2 "NIST Guide to the SI, Chapter 5: Units Outside the SI". NIST. January 28, 2016.

[2] "Details of SI units". sizes.com. 2011-07-01. Retrieved 2011-10-04.

[SI-brochure-3] 1 2 The International System of Units (PDF), V4.01 (9th ed.), International Bureau of Weights and Measures, Jun 2026, ISBN 978-92-822-2272-0

[4] A Dictionary of Earth Sciences (3 ed.). Oxford University Press. January 1, 2008. doi:10.1093/acref/9780199211944.001.0001. ISBN 978-0-19-921194-4."gamma". www.oxfordreference.com. Oxford, UK: Oxford University Press. Retrieved 2026-06-07.

[5] McGraw Hill Encyclopaedia of Physics (2nd edition), C. B. Parker, 1994, ISBN 0-07-051400-3.^{[page needed]}

[6] "SI base unit: ampere (A)". www.bipm.org. Sevres, France: Bureau International des Poids et Mesures. 2019. Retrieved 2026-06-07."Historical perspective: Unit of electric current, ampere". www.bipm.org. Sevres, France: Bureau International des Poids et Mesures. 2019. Retrieved 2026-06-07.

[7] Shisong Li; Qing Wang; Wei Zhao; Songling Huang (2020-07-20). "From μ₀ to e: A Survey of Major Impacts for Electrical Measurements in Recent SI Revision". ieeexplore.ieee.org. IEEE. Retrieved 2026-06-10.

[8] "Ronald B. Goldfarb" (2017). "The Permeability of Vacuum and the Revised International System of Units". ieeexplore.ieee.org. IEEE. Retrieved 2026-06-10.

[GeomagneticReferenceField-9] Finlay, C. C.; Maus, S.; Beggan, C. D.; Bondar, T. N.; Chambodut, A.; Chernova, T. A.; Chulliat, A.; Golovkov, V. P.; Hamilton, B.; Hamoudi, M.; Holme, R.; Hulot, G.; Kuang, W.; Langlais, B.; Lesur, V.; Lowes, F. J.; Lühr, H.; Macmillan, S.; Mandea, M.; McLean, S.; Manoj, C.; Menvielle, M.; Michaelis, I.; Olsen, N.; Rauberg, J.; Rother, M.; Sabaka, T. J.; Tangborn, A.; Tøffner-Clausen, L.; Thébault, E.; Thomson, A. W. P.; Wardinski, I.; Wei, Z.; Zvereva, T. I. (December 2010). "International Geomagnetic Reference Field: the eleventh generation". Geophysical Journal International. 183 (3): 1216–1230. Bibcode:2010GeoJI.183.1216F. doi:10.1111/j.1365-246X.2010.04804.x. hdl:20.500.11850/27303.

[10] "EMF: 7. Extremely low frequency fields like those from power lines and household appliances". ec.europa.eu. Archived from the original on 2021-02-24. Retrieved 2022-05-13.

[11] "Ultra-High Field". Bruker BioSpin. Retrieved 4 October 2011.{{cite web}}: CS1 maint: deprecated archival service (link)

[12] "Superconducting Magnet in CMS". Retrieved 9 February 2013.

[13] "The Strongest Permanent Dipole Magnet" (PDF). Retrieved 2 May 2020.

[14] "ISEULT – INUMAC". Retrieved 17 February 2014.

[15] "ITER – the way to new energy". Retrieved 19 April 2012.

[16] Hesla, Leah (13 July 2020). "Fermilab achieves 14.5-tesla field for accelerator magnet, setting new world record". Retrieved 13 July 2020.

[17] Berry, M. V.; Geim, A. K. (1997). "Of Flying Frogs and Levitrons" by M. V. Berry and A. K. Geim, European Journal of Physics, v. 18, 1997, p. 307–13" (PDF). European Journal of Physics. 18 (4): 307–313. doi:10.1088/0143-0807/18/4/012. S2CID 1499061. Archived from the original (PDF) on 8 October 2020. Retrieved 4 October 2020.

[18] "The 2000 Ig Nobel Prize Winners". August 2006. Retrieved 12 May 2013.)

[19] "Superconductor Traps The Strongest Magnetic Field Yet". 2 July 2014. Retrieved 2 July 2014.

[20] Hartwig, Zachary S. (March 2024). "The SPARC Toroidal Field Model Coil Program". IEEE Transactions on Applied Superconductivity. 34 (2): 1–16. arXiv:2308.12301. doi:10.1109/TASC.2023.3332613. ISSN 1051-8223.

[MagnetLab-21] 1 2 "Mag Lab World Records". Media Center. National High Magnetic Field Laboratory, USA. 2008. Retrieved 24 October 2015.

[22] "World record pulsed magnetic field". Physics World. 31 August 2011. Retrieved 26 January 2022.)

[23] D. Nakamura, A. Ikeda, H. Sawabe, Y. H. Matsuda, and S. Takeyama (2018), Magnetic field milestone

v t e SI units
Base units	ampere candela kelvin kilogram metre mole second
Derived units with special names	becquerel coulomb degree Celsius farad gray henry hertz joule katal lumen lux newton ohm pascal radian siemens sievert steradian tesla volt watt weber
See also	International System of Units Historical definitions of the SI base units 2019 revision of the SI Metric prefixes Conversion of units System of units of measurement
Category

v t e Nikola Tesla
Career and inventions	Patents Plasma lamp plasma globe Polyphase system Alternating-current commutatorless induction motor Tesla Experimental Station Teleforce Telegeodynamics Tesla coil history Wireless power Resonant inductive coupling Radio control Tesla turbine Tesla's oscillator Tesla valve Three-phase electric power Wardenclyffe Tower Tesla Electric Light and Manufacturing
Writings	The Inventions, Researches, and Writings of Nikola Tesla Colorado Springs Notes, 1899–1900 "Fragments of Olympian Gossip" My Inventions: The Autobiography of Nikola Tesla
Other	War of the currents Westinghouse Electric World Wireless System In popular culture
Related	Nikola Tesla Museum Nikola Tesla Memorial Center Tesla Science Center at Wardenclyffe IEEE Nikola Tesla Award Tesla Satellite Award Belgrade Nikola Tesla Airport New Yorker Hotel The Secret of Nikola Tesla (1980 film) Tesla – Lightning in His Hand (2003 opera) The Prestige (2006 film) Tower to the People (2015 documentary) Tesla (2016 film) The Tesla World Light (2017 film) The Current War (2019 film) "Nikola Tesla's Night of Terror" (2020 TV episode) Tesla (2020 film) Tesla: Man Out of Time Wizard: The Life and Times of Nikola Tesla The Man Who Invented the Twentieth Century Boat SI derived unit Lunar crater Asteroid Tesla, Inc.