The tesla is the SI unit of magnetic flux density.
The unit measures how much magnetic flux passes through a given area, with the field oriented perpendicular to that area. One tesla equals one weber per square metre. It can also be expressed as one newton per ampere-metre, linking magnetic fields to the force on a current-carrying conductor.
The unit honors Nikola Tesla, the Serbian-American inventor and electrical engineer. The General Conference on Weights and Measures adopted the tesla as an SI derived unit in 1960. It is symbolized by T.
A common mix-up is between the tesla and the weber: the weber measures total magnetic flux, while the tesla measures flux density. The older gauss remains common in some contexts, but one tesla equals 10,000 gauss.