What Are Minutes?

Minutes are units of measurement used to subdivide the degree in angular measurement and the hour in time measurement. Both uses share the same sexagesimal (base-60) structure inherited from Babylonian astronomy, in which each primary unit divides into 60 equal parts. In engineering and science, minutes appear in navigation, geodesy, astronomy, control systems, and signal timing, wherever a resolution finer than a degree or an hour is required but the full precision of arc seconds or seconds of time is not needed.

The two meanings are formally distinct. A minute of time equals exactly 60 seconds, while a minute of arc (also written arcminute, abbreviated arcmin or with the prime symbol ′) equals one-sixtieth of one degree of angle. Both are non-SI units, yet both are accepted for use alongside the International System of Units as documented by the BIPM because they remain deeply embedded in navigation, timekeeping, and astronomy standards.

Minutes of Time

As a unit of time, the minute equals 1/60 of an hour, or 60 SI seconds. The second is the SI base unit of time, defined in terms of the cesium-133 hyperfine transition frequency; the minute and hour are derived from it by fixed multiplying factors. In engineering contexts, minutes appear in rate and throughput specifications (revolutions per minute, packets per minute, samples per minute) and in scheduling systems where human-readable intervals matter more than SI purity. Precision timekeeping at the level of milliseconds and below uses seconds, but higher-level system specifications for network latency, production throughput, and control-loop periods routinely express intervals in minutes.

Minutes of Arc

A minute of arc is one-sixtieth of a degree, or equivalently 1/21,600 of a full circle. It subdivides further into 60 arcseconds. As noted by the San Diego State University atmospheric optics reference, the angular diameter of the full Moon is approximately 30 arcminutes, and human visual acuity reaches roughly 1 arcminute. In navigation, geographic coordinates are expressed in degrees, minutes, and decimal seconds (DMS format), so latitude and longitude readings to the arcminute correspond to approximately 1.85 km of ground distance at the equator. In astronomy, telescope resolving power and the separation of double stars are commonly stated in arcminutes or arcseconds.

Precision and Instrument Resolution

Instruments that report angular positions use arcminutes to express accuracy and resolution. Theodolites, total stations, and inertial measurement units specify their angular noise floors and systematic errors in arcminutes or arcseconds. A surveying instrument with one-arcminute angular accuracy can resolve a positional difference of about 29 mm at 100 m range. In optical systems, the resolving limit of human vision at one arcminute motivates display design standards: a pixel angular subtense near one arcminute is sufficient to produce a perceptually continuous image. EarthSky's guide to sky measurements illustrates how professional and amateur observers apply arcminute-scale reasoning to observe and measure celestial objects.

Applications

Minutes, as units of both time and arc, have applications across a wide range of technical fields, including:

• Navigation and GPS coordinate systems expressing geographic position in degrees and minutes
• Astronomy for cataloging star positions, angular separations, and telescope field-of-view specifications
• Geodesy and land surveying for angular measurements and coordinate transformations
• Industrial control systems expressing machine rotation rates in revolutions per minute
• Optical instrument design and display engineering based on human visual acuity limits