A "milliradian" is 1/1000 of a radian.
Most people who do mathematics or physics use radians, rather than degrees, because some kinds of calculations, mostly in trigonometry and calculus, are simpler when using radians rather than degrees.
1 radian is equal to about 57.3°. There are 2π radians (about 6.28 radians) in a full circle. The formula for turning radians to degrees and vice versa is:
we can also say: