Arcminute (′)

General & non-SICurrent unit

One sixtieth of a degree. Used in navigation, astronomy and rifle sighting (minute of angle).

1 arcminute = 0.0000462962963 turns (approximately).

About the arcminute

An arcminute is a sixtieth of a degree, which makes it 1/21,600 of a turn or about 0.29 milliradian. The SI Brochure lists it among widely used non-SI units, equal to π/10,800 radian. The units come from Babylonian astronomy and its habit of splitting the degree into 60 parts.

It is a handy size for everyday precision. One arcminute of latitude is roughly one nautical mile, and navigation often writes positions in degrees and decimal minutes. Someone with 20/20 vision can just resolve details about an arcminute apart. The Sun and the Moon each measure around 30 to 32 arcminutes across. Property surveyors use degrees, minutes, and seconds in metes-and-bounds boundary descriptions. Shooters call the unit minute of angle, or MOA, where 1 MOA covers about 1.047 inches at 100 yards.

Sources: BIPM SI Brochure, 9th edition (2019); Wikipedia: Minute and second of arc; Wikipedia: Angular diameter

Arcminute conversion chart

1 arcminute expressed in every other angle unit:

More General & non-SI units

• degree (angle)
• gradian (angle)
• turn (angle)
• arcsecond (angle)
• right angle (angle)
• octant (angle)
• sextant (angle)
• piece (counting & quantity)
• pair (counting & quantity)
• score (counting & quantity)
• hundred (counting & quantity)
• thousand (counting & quantity)
• million (counting & quantity)
• billion (short scale) (counting & quantity)
• trillion (short scale) (counting & quantity)
• billion (long scale) (counting & quantity)

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