rad | OptoWiki Knowledge Base

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

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