Magnetic Units

Download this table as a PDF formatted for print.

Quantity	Symbol	Gaussian & cgs emu ^a	Conversion factor, C ^b	SI & rationalized mks ^c
Magnetic flux density, magnetic induction	B	gauss (G) ^d	10^-4	tesla (T), Wb/m²
Magnetic flux	Φ	maxwell (Mx), Gּcm²	10^-8	weber (Wb), volt second (Vּs)
Magnetic potential difference,magnetomotive force	U, F	gilbert (Gb)	10/4π	ampere (A)
Magnetic field strength, magnetizing force	H	oersted (Oe),^eGb/cm	10³/4π	A/m ^f
(Volume) magnetization ^g	M	emu/cm^3 h	10³	A/m
(Volume) magnetization	4πM	G	10³/4π	A/m
Magnetic polarization, intensity of magnetization	J, I	emu/cm³	4π x 10^-4	T, Wb/m² ⁱ
(Mass) magnetization	σ, M	emu/g	1 4π x 10^-7	Aּm²/kg Wbּm/kg
Magnetic moment	m	emu, erg/G	10^-3	Aּm², joule per tesla (J/T)
Magnetic dipole moment	j	emu, erg/G	4π x 10^-10	Wbּm ⁱ
(Volume) susceptibility	χ, κ	dimensionless, emu/cm³	4π (4π)² x 10^-7	dimensionless henry per meter (H/m), Wb/(Aּm)
(Mass) susceptibility	χ_ρ, κ_ρ	cm³/g, emu/g	4π x 10^-3 (4π)² x 10^-10	m³/kgHּm²/kg
(Molar) susceptibility	χ_m, κ_mol	cm³/mol, emu/mol	4π x 10^-6 (4π)² x 10^-13	m³/molHּm²/mol
Permeability	μ	dimensionless	4π x 10^-7	H/m, Wb/(Aּm)
Relative permeability ^j	μ_r	not defined	-	dimensionless
(Volume) energy density, energy product ^k	W	erg/cm³	10^-1	J/m³
Demagnetization factor	D, N	dimensionless	1/4π	dimensionless
a. Gaussian units and cgs emu are the same for magnetic properties. The defining relation is B = H + 4πM. b. Multiply a number in Gaussian units by C to convert it to SI (e.g., 1 G x 10^-4 T/G = 10^-4 T). c. SI (Système International d’Unitès) has been adopted by the National Bureau of Standards.Where to conversion factors are given, the upper one is recognized under, or consistent with, SI and is based on the definition B = μ_o(H + M), where μ_o = 4π x 10^-7 H/m. The lower one is not recognized under SI and is based on the definition B = μ_oH + J, where the symbol I is often used in place of J. d. 1 gauss = 10⁵gamma (γ). e. Both oersted and gauss are expressed as cm^-1/2ּg^1/2ּs^-1 in terms of base units. f. A/m was often expressed as “ampere-turn per meter” when used for magnetic field strength. g. Magnetic moment per unit volume. h. The designation “emu” is not a unit. i. Recognized under SI, even though based on the defition B = μ_oH + J. See footnote c. j. μ_r = μ/μ_o = 1 + χ, all in SI. μ_r is equal to Gaussian μ. k. BּH and μ_oMּH have SI units J/m³; MּH and BּH/4π have Gaussian units erg/cm³.

This information was taken with permission from R. B. Goldfarb and F. R. Fickett, U.S. Department of Commerce, National Bureau of Standards, Boulder, Colorado 80303, March 1985, NBS Special Publication 696.