The oersted (abbreviated as Oe) is the unit of magnetic field strength |H| in the cgs-emu (centimeter-gram-second electromagnetic unit) system of units. The field strength in a point in vacuum is 1 Oe if a unit magnetic pole in the point experiences a force of 1 dyne ( = 1⋅10−5 newton). The cgs-emu defining equation of the oersted is: Oe = cm−1/2 g1/2 s−1. The oersted is also the unit of magnetic field strength in the system of Gaussian units.
In agreement with the Biot-Savart law one may also define one oersted as the magnetic field strength |H| in the center of a conducting loop with radius of 1 cm, carrying a current of 10/(2π) A.
One oersted equals 1000/4π A/m (ampere per meter, which is the SI unit for |H|).
The oersted is named after the Danish physicist Hans Christian Oersted. Before 1932 the oersted was known as gauss, a name sometimes still applied, though now more properly used for the cgs-emu unit of strength of magnetic induction |B|.