CGS System of Units Converter
Convert between SI and CGS units for force, energy, pressure, viscosity, magnetic fields and more.
CGS and SI equivalents
| CGS | SI | Factor |
|---|---|---|
| Centimetre (cm) | metre (m) | 1 cm = 0.01 m |
| Gram (g) | kilogram (kg) | 1 g = 0.001 kg |
| Dyne (dyn) | newton (N) | 1 dyn = 1.0e-5 N |
| Erg (erg) | joule (J) | 1 erg = 1.0e-7 J |
| Erg per second (erg/s) | watt (W) | 1 erg/s = 1.0e-7 W |
| Barye (Ba) | pascal (Pa) | 1 Ba = 0.1 Pa |
| Poise (P) | pascal-second (Pa·s) | 1 P = 0.1 Pa·s |
| Stokes (St) | square metre per second (m²/s) | 1 St = 0.0001 m²/s |
| Gauss (G) | tesla (T) | 1 G = 0.0001 T |
| Maxwell (Mx) | weber (Wb) | 1 Mx = 1.0e-8 Wb |
| Oersted (Oe) | ampere per metre (A/m) | 1 Oe = 79.5775 A/m |
| Statcoulomb (statC) | coulomb (C) | 1 statC = 3.33564e-10 C |
| Gal (Gal) | metre per second squared (m/s²) | 1 Gal = 0.01 m/s² |
| Reciprocal centimetre (cm⁻¹) | reciprocal metre (m⁻¹) | 1 cm⁻¹ = 100 m⁻¹ |
What CGS is
CGS builds its units from the centimetre, gram and second instead of SI's metre, kilogram and second. Because the base units are 100 and 1,000 times smaller, the derived units come out much smaller too — a dyne is 10−5 newtons and an erg is 10−7 joules.
SI replaced it for general use decades ago, but CGS survives where its magnitudes are convenient: astronomy quotes luminosities in erg/s, spectroscopists work in cm−1, and gauss is still the everyday unit for magnets.
The mechanical units are simple powers of ten
Force, energy, pressure and viscosity all convert by exact powers of ten, so the arithmetic is just moving a decimal point:
1 dyn = 10⁻⁵ N
1 erg = 10⁻⁷ J
1 Ba = 0.1 Pa
1 P = 0.1 Pa·s
The electromagnetic units are not
This is where CGS gets genuinely awkward. Gaussian units fold the constant 4π into the definitions of the fields themselves, so magnetic conversions carry factors like 1000/4π, and the statcoulomb is tied to the speed of light rather than to the ampere. There are also several competing CGS electromagnetic systems — electrostatic, electromagnetic and Gaussian — which do not agree with each other.
The values here follow the Gaussian convention, the most commonly encountered one. If you are converting from an older text, check which system it uses before trusting a factor.
Because the 4π is placed differently, some CGS formulas look structurally different from their SI counterparts rather than just differing by a constant. Converting a whole equation needs more care than converting one number.