# Constants (API)

Constants have been defined for use in expressions and calculations.

## Constants

The constants are accessed as illustrated below.

cf.Const.<const option>
c0
Speed of light in free space in m/sec. The value of c0 is 299792458.000176.
eps0
Permittivity of free space in F/m. The value of eps0 is 8.854187817609999e-12.
mu0
Permeability of free space in H/m. The value of mu0 is 1.25663706143592e-06.
pi
Mathematical constant pi (Ludolph's number). The value of pi is 3.141592653589793.
zf0
Characteristic impedance of free space in Ohm. The value of zf0 is 376.730313461992.