Magnitude is included by default in each file as part of the Math library.
The Magnitude() function returns the unitless component of a number.
Typically Magnitude() is not the best way to "strip" units from a number. This is because if the number gets converted along the way, you will get a different answer.
The better method to strip units is to divide by 1 using the unit you expect. This is covered on the units page.
Magnitude(6.2 ft) = 6.2
Magnitude(1 ft to in) = 12
Magnitude(5.3) = 5.3