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SI Brochure: The International System of Units (SI)
Non-SI units accepted for use with the SI, and units based on fundamental constants (contd.)
SI Brochure, from Section 4.1

    Table 9 differs from Table 8 only in that the units in Table 9 are related to the older CGS (centimetre-gram-second) system of units, including the CGS electrical units. In the field of mechanics, the CGS system of units was built upon three quantities and their corresponding base units: the centimetre, the gram, and the second. The CGS electrical units were still derived from only these same three base units, using defining equations different from those used for the SI. Because this can be done in different ways, it led to the establishment of several different systems, namely the CGS-ESU (electrostatic), the CGS-EMU (electromagnetic), and the CGS-Gaussian unit systems. It has always been recognized that the CGS-Gaussian system, in particular, has advantages in certain areas of physics, particularly in classical and relativistic electrodynamics (9th CGPM, 1948, Resolution 6). Table 9 gives the relations between these CGS units and the SI, and lists those CGS units that were assigned special names. As for the units in Table 8, the SI prefixes are used with several of these units (e.g. millidyne, mdyn; milligauss, mG, etc.).

    Table 9. Non-SI units associated with the CGS and the CGS-Gaussian system of units

    Quantity Name of unit Symbol for unit Value in SI units
    energy erg (a) erg 1 erg = 10–7 J
    force dyne (a) dyn 1 dyn = 10–5 N
    dynamic viscosity poise (a) P 1 P = 1 dyn s cm–2 = 0.1 Pa s
    kinematic viscosity stokes St 1 St = 1 cm2 s–1 = 10–4 m2 s–1
    luminance stilb (a) sb 1 sb = 1 cd cm–2 = 104 cd m–2
    illuminance phot ph 1 ph = 1 cd sr cm–2 = 104 lx
    acceleration gal (b) Gal 1 Gal = 1 cm s–2 = 10–2 m s–2
    magnetic flux maxwell (c) Mx 1 Mx = 1 G cm2 = 10–8 Wb
    magnetic flux density gauss (c) G 1 G = 1 Mx cm–2 = 10–4 T
    magnetic field œrsted (c) Oe 1 Oe corresponds to (103/4pi) A m–1

    (a) This unit and its symbol were included in Resolution 7 of the 9th CGPM (1948).
    (b) The gal is a special unit of acceleration employed in geodesy and geophysics to express acceleration due to gravity.
    (c) These units are part of the so-called "electromagnetic" three-dimensional CGS system based on unrationalized quantity equations, and must be compared with care to the corresponding unit of the International System which is based on rationalized equations involving four dimensions and four quantities for electromagnetic theory. The magnetic flux, phi, and the magnetic flux density, B, are defined by similar equations in the CGS system and the SI, so that the corresponding units can be related as in the table. However, the unrationalized magnetic field, H (unrationalized) = 4pi x H (rationalized). The equivalence symbol corresponds to is used to indicate that when H (unrationalized) = 1 Oe, H (rationalized) = (103/4pi) A m–1.
    		 

We are pleased to present the 9th edition of the SI Brochure (2019), which defines and presents the Système International d'Unités, the SI (known in English as the International System of Units).
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