Mil (NATO) (mil)

MilitaryCurrent unit

One 6,400th of a full turn (0.05625 degree). The NATO standard for artillery and sighting.

1 mil (NATO) = 0.00015625 turns (exactly).

About the mil (NATO)

The NATO mil divides the circle into 6,400 parts, so each is 0.05625 degree, or about 0.98 milliradian. NIST lists the angular mil at exactly 0.05625 degree, about 9.817 × 10⁻⁴ radian, which works out to roughly 0.98 meter at a distance of 1 kilometer. A true milliradian is a thousandth of a radian, so a true circle holds about 6,283. The figure 6,400 is a deliberate rounding to a number that divides easily: a quarter turn is exactly 1,600 mils.

The system came from France. Around the start of World War I, French artillery tested millièmes, 6,400 to the circle, in place of decigrades, which put 4,000 in a circle, and then adopted them. The United States later copied French artillery practice, and NATO standardized the unit in the 1950s as it moved to metric measurements. Other forces use different circles, such as the 6,000-mil circle of the Soviet system.

Sources: NIST Guide to the SI, Appendix B.8 (angle conversion factors); Wikipedia: Angular mil; Wikipedia: Milliradian

Mil (NATO) conversion chart

1 mil (NATO) expressed in every other angle unit:

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