Wolfram|Alpha
zum Thema Lichtgeschwindigkeit:

c (speed of light in vacuum)

Value:

299792 km/s (kilometers per second)
2.998x10^8 m/s (meters per second)

Comparison:
~~ 2.4 x speed of light in diamond
(~~ 1.24x10^8 m/s )

Interpretation:
speed

Basic unit dimensions:
[length] [time]^(-1)

Corresponding quantity:
Slowness from S = 1/v:\n | 3.336x10^-9 s/m (seconds per meter)