# Constants - Orbifold/XAct GitHub Wiki

The **Constants** class contains all sorts of mathematical, numerical and useful constants.

- Catalan: the Catalan number
- Euler: the Euler constant
- EulerGamma: the Euler-Mascheroni constant
- Glaisher: the Glaisher-Kinkelin constant
- GoldenRatio: the golden ratio
- InverseEuler: the inverse of the Euler constant (i.e. 1/e)
- InversePi: the inverse of Pi (i.e. 1/pi)
- InvSqrt2Pi: the inverse of square root of twice pi ( i.e. 1/Sqrt(2*Pi))
- InvSqrtPi: the inverse of the square root of Pi(i.e. 1/Sqrt(Pi))
- Khinchin: the Khinchin constant
- Log2E: the log of the Euler constant in base 2 (i.e. log(2)(e))
- Ln2: the log of two in the natural base (i.e. log(e)(2))
- Ln10: the log of ten in the natural base (i.e. log(e)(10))
- LnPi: the log of pi in the natural base (i.e. log(e)(10))
- Pi: the pi constant (150 digits precision)
- Sqrt1Over2: the square root of 0.5
- Sqrt2: the square root of two
- Sqrt2Pi: the square root of twice pi
- Sqrt3DividedBy2: the square root of three divided by two
- PiOver180: pi divided by 180 (the degree to radians conversion factor)
- PiOver2: pi divided by 2
- SqrtPi: the square root of pi
- PiOver4: pi divided by 4
- SpeedOfLight: the speed of light in vacuum
- PlancksConstant: the Planck constant
- PlancksLength: the Planck length
- GravitationalConstant: the gravitational constant
- MagneticPermeability: the magnetic permeability in vacuum
- ElectricPermitivity: the electric permitivity in vacuum