2 A B C D E F G H I K L M N O P R S T U V W
Ra Re
Rad Ran Ray

rad

for a circle of radius r is ‘1 rad’ the angle corresponding to length r on the circle,

say
1\,\mathrm{rad} = \frac {360^\circ} {2 pi} = \frac {180^\circ} {\pi} \approx 57{,}29577951^\circ

accordingly :
1\,\mathrm{mrad} = \frac {1 rad} {1000} :

1\,\mathrm{mrad} = \frac {360^\circ} {2000 \pi} = \frac {180^\circ} {1000 \pi} \approx 0{,}05729577951^\circ