The tesla (symbol T) is the SI derived unit of magnetic field (specifically magnetic flux density). The tesla is equal to one weber per square metre and was defined in 1960 in honor of inventor, scientist and electrical engineer Nikola Tesla.
This SI unit is named after Nikola Tesla. As with all SI units whose names are derived from the proper name of a person, the first letter of its symbol is uppercase (T). But when an SI unit is spelled out, it should always be written in lowercase (tesla), unless it begins a sentence or is the name "degree Celsius".
— Based on The International System of Units, section 5.2.
1 tesla is equivalent to:
10,000 (or 104) gauss (G), used in CGS system. Thus, 10G = 1mT (1 millitesla)
1,000,000,000 (or 109) gammas (γ), used in geophysics. Thus, 1γ = 1nT (nanotesla)
In September 2006, NASA found "potholes" in the magnetic field in the heliosheath around our solar system that are 10 picoteslas as reported by Voyager 1
In outer space the magnetic field is between 0.1 and 10 nanoteslas (10−10 T and 10−8 T)
Earth's magnetic field at latitude of 50° is 58 µT (5.8×10−5 T) and on the equator at a latitude of 0° is 31 µT (3.1×10−5 T)
In a sunspot, the magnetic field is about 150 mT
A large 14 kg loudspeaker magnet has a coil gap of 1 T.