**Speed of light in vacuum** is a unit of measurement of speed. The definition for speed of light in vacuum is the following:

The speed of light in vacuum is equal to 299792458 metres (meters) per second.

The speed of light is a physical constant representing the speed at which light (or any other electromagnetic radiation) travels in vacuum. It is usually denoted by the symbol c and it is equal to exactly 299,792,458 metres per second (299792.458 kilometres per second or approximately 186,282 miles per second). The speed of light constant appears in the famous equation of the theory of relativity, **E = m.c**^{2} (where E is energy, m is the mass of an object and c is the speed of light constant).

The symbol for speed of light in vacuum is

**c**Speed of light in vacuum is compatible with the

meter per second base unit.