Guide for the Use of the International System of Units (SI)

5.3 Units not accepted for use with the SI 
The following two sections briefly discuss units not accepted for use with the SI. 
 
5.3.1 CGS units 
Table 10 gives examples of centimeter-gram-second (CGS) units having special names. These units 
are not accepted for use with the SI by this Guide. Further, no other units of the various CGS systems of 
units, which includes the CGS Electrostatic (ESU), CGS Electromagnetic (EMU), and CGS Gaussian 
systems, are accepted for use with the SI by this Guide except such units as the centimeter, gram, and 
second that are also defined in the SI. 

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Guide for the Use of the International System of Units (SI) 
 
11 
Table 10. Examples of CGS units with special names (not accepted for use with the SI by this Guide) 
Name 
Symbol 
Value in SI units 
erg 
dyne 
poise
(a)
stokes
(b)
gauss
(c)
oersted
(c)
maxwell
(c)
stilb 
phot 
gal
(d)
erg 
dyn 
P 
St 
Gs, 
G 
Oe 
Mx 
sb 
ph 
Gal 
1 erg = 10
−7
J 
1 dyn = 10
−5
N 
1 P = 1 dyn · s/cm
2
= 0.1 Pa · s 
1 St = 1 cm
2
/s = 10
−4
m
2
/s 
1 Gs corresponds to 10
−4
T 
1 Oe corresponds to (1000/4π) A/m 
1 Mx corresponds to 10
−8 
Wb 
1 sb = 1 cd/cm
2 
= 10
4
cd/m
2
1 ph = 10
4
lx 
1 Gal = 1 cm s
−2
= 10
−2
m s
−2
(a) The poise (P) is the CGS unit for viscosity (also called dynamic viscosity). The SI unit is the pascal second (Pa · s). 
(b) The stokes (St) is the CGS unit for kinematic viscosity. The SI unit is the meter squared per second (m
2
/s). 
(c) This unit is part of the so-called electromagnetic three-dimensional CGS system and cannot strictly speaking be compared to the 
corresponding SI unit, which has four dimensions when only mechanical and electric quantities are considered. 
(d) The gal is employed in geodesy and geophysics to express acceleration due to gravity.