Magnetic Units

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),^e Gb/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/m^{2 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/kg
Hּm²/kg

(Molar) susceptibility

χ_m, κ_mol

cm³/mol, emu/mol

4π x 10^-6
(4π)² x 10^-13

m³/mol
Hּm²/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 = 10⁵ gamma (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.