Here's why:

* Speed is a scalar quantity, meaning it only has magnitude (how fast something is moving).

* Velocity is a vector quantity, meaning it has both magnitude and direction (how fast something is moving and in what direction).

Therefore, the magnitude of speed is the same as the speed itself. There's no need to calculate anything further.

Example:

* A car traveling at 60 mph has a speed of 60 mph. The magnitude of its speed is also 60 mph.