A minute of arc, arcminute, or minute arc (MOA), is a unit of angular measurement equal to one sixtieth (¹⁄₆₀) of one degree (^circle⁄_21,600), or (^π⁄_10,800) radians. In turn, a second of arc or arcsecond is one sixtieth (¹⁄₆₀) of one minute of arc. Since one degree is defined as one three hundred and sixtieth (¹⁄₃₆₀) of a rotation, one minute of arc is ¹⁄_21,600 of a rotation. It is used in those fields which require a unit for the expression of small angles, such as astronomy, navigation and marksmanship.

The number of square arcminutes in a complete sphere is

or approximately 148,510,660.498 square arcminutes.

The arcsecond is ¹⁄_3,600 of a degree, or ¹⁄_1,296,000 of a circle, or (^π⁄_648,000) radians, which is approximately ¹⁄_206,265 radian.

To express even smaller angles, standard SI prefixes can be employed; in particular, the milliarcsecond, abbreviated mas, is used in astronomy.

The standard symbol for marking the arcminute is the prime (′) (U+2032), though a single quote (') (U+0027) is commonly used where only ASCII characters are permitted. One arcminute is thus written 1′. It is also abbreviated as arcmin or amin or, less commonly, the prime with a circumflex over it (Failed to parse (Missing texvc executable; please see math/README to configure.): \hat{'} ).