How this calculator works
The centimetre-gram-second system builds mechanical units from the centimetre, gram and second instead of the metre, kilogram and second. It is still used in astronomy, materials science and older scientific literature, where the erg, dyne, poise, stokes, gauss and oersted remain familiar. Mechanical conversions are powers of ten because the base units differ by powers of ten. Electromagnetic quantities are not so simple: the CGS system has electrostatic and electromagnetic branches, and the charge and voltage units shown here use the Gaussian electrostatic definitions.
Formula
CGS value = SI value x F, where F is: acceleration 100 Gal per m/s²; force 100,000 dyn per N; energy 10,000,000 erg per J; pressure 10 Ba per Pa; dynamic viscosity 10 P per Pa·s; kinematic viscosity 10,000 St per m²/s; charge 2.99792458 x 10^9 statC per C; voltage 1/299.792458 statV per V; magnetic B 10,000 G per T; magnetic H 4 pi/1,000 Oe per A/m. Divide to go back to SI.
Worked example
1 N is 100,000 dyn. 1 J is 10,000,000 erg. 1 Pa·s is 10 poise, and 1 centipoise is 0.001 Pa·s. 1 T is 10,000 gauss. 1 A/m is about 0.012566 oersted, so 1 oersted is about 79.577 A/m.
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Frequently asked questions
Why is the CGS system still used?
Some fields kept units that are convenient at their scale. An astronomer measures in ergs and gauss, and a materials scientist often reports viscosity in poise and centistokes. The system is also compact in older papers, so conversions remain necessary.
Why do charge and voltage use 299,792,458 in their factors?
The Gaussian electrostatic system defines charge through Coulomb's law with the speed of light built in. That is why one statcoulomb is not a round number of coulombs and one statvolt is not a round number of volts.
Is the poise a unit of dynamic or kinematic viscosity?
The poise is dynamic viscosity, the CGS counterpart of the pascal second. The stokes is kinematic viscosity, the counterpart of square metres per second. Centipoise and centistokes are one hundredth of each and are common in oil specifications.