mrad
milliradian
Angleexact by definition
The milliradian is one thousandth of a radian, about 0.0573 degrees. Its usefulness is the small-angle approximation: at one kilometre a milliradian subtends one metre, so a 3 mrad laser divergence spreads to a 3 m spot at that range. Beam divergence, machine alignment and optical wedge angles are all specified in mrad.
Watch out: Rifle scopes marked in "mils" or "MIL" use the true milliradian, 6,283.19 to a full turn, while artillery uses the NATO mil of 6,400 to a turn. The two differ by about 1.9%, which matters at long range. Note also that MOA, the other shooting unit, is a minute of arc and about 3.4 times smaller than a milliradian.
| 1 mrad | 0.05729578 ° |
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