CGS System of Units Converter

What is the CGS System of Units Converter?

The CGS System of Units Converter is a free online tool that converts physical quantities between the CGS (centimeter-gram-second) system and the SI (International System of Units). It covers acceleration, force, energy, pressure, dynamic and kinematic viscosity, electric charge, voltage, and magnetic field strengths. For other unit conversions, check our Unit Converter and Force Converter.

What is the CGS System?

The CGS system (centimeter-gram-second) is a metric system of measurement that uses the centimeter as the unit of length, the gram as the unit of mass, and the second as the unit of time. It was widely used in physics before the adoption of the SI system. Many fundamental physical constants and equations are still expressed in CGS units in scientific literature, particularly in electromagnetism and condensed matter physics.

Key CGS Units and Their SI Equivalents

Acceleration: 1 Gal (galileo) = 0.01 m/s²
Force: 1 dyne (dyn) = 10⁻⁵ N
Energy: 1 erg = 10⁻⁷ J
Pressure: 1 barye (Ba) = 0.1 Pa
Dynamic Viscosity: 1 poise (P) = 0.1 Pa·s
Kinematic Viscosity: 1 stokes (St) = 10⁻⁴ m²/s
Electric Charge: 1 franklin (Fr) = 3.336×10⁻¹⁰ C
Voltage: 1 statvolt (statV) = 299.792458 V
Magnetic Field B: 1 gauss (G) = 10⁻⁴ T
Magnetic Field H: 1 oersted (Oe) = 79.57747 A/m

Why Use CGS Units?

The CGS system simplifies many electromagnetic equations by setting the permittivity and permeability of free space to 1 (dimensionless). This makes it popular in theoretical physics, quantum mechanics, and solid-state physics. For example, Coulomb's law in CGS is simply $F = q_1q_2/r^2$ without the $1/4\pi\epsilon_0$ factor needed in SI units.

How to Use This Converter

Select the quantity type from the dropdown menu (acceleration, force, energy, etc.).
Enter a value in either the CGS or SI input field.
The other field updates automatically with the converted value.
View physical constants in the reference section for additional scientific context.

Frequently Asked Questions

Why does the CGS system have different units for electromagnetism?

The CGS system uses different definitions for electromagnetic quantities because it sets the Coulomb constant $k_e = 1$ (dimensionless), unlike SI which uses $k_e = 1/4\pi\epsilon_0$. This means the CGS system has multiple subsystems (ESU, EMU, Gaussian) for electromagnetism, each with different conversion factors.

What is the difference between CGS and MKS systems?

The MKS (meter-kilogram-second) system is essentially the mechanical part of the SI system. While MKS uses meters and kilograms, CGS uses centimeters and grams. Both use seconds for time. The conversion is purely a matter of scaling: 1 m = 100 cm, 1 kg = 1000 g.

Is the CGS system still used today?

Yes, the CGS system is still commonly used in specific scientific fields. Astronomers use CGS for stellar astrophysics, condensed matter physicists use it for semiconductor research, and it appears frequently in older scientific papers. Many fundamental constants like the Bohr radius and fine-structure constant are often quoted in CGS units.

What does "gal" stand for in CGS acceleration?

The gal (or galileo, symbol Gal) is the CGS unit of acceleration named after Galileo Galilei. It is used primarily in gravimetry and geophysics for measuring gravitational acceleration. One gal equals 1 cm/s², or 0.01 m/s².

How do I convert between different CGS subsystems for electromagnetism?

There are three main CGS subsystems for electromagnetism: electrostatic (ESU), electromagnetic (EMU), and Gaussian. The Gaussian system is the most common, combining ESU for electric quantities and EMU for magnetic quantities. Our converter uses Gaussian CGS units for all electromagnetic conversions.

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