Kiertoaikaa

Kiertoaika, translated as orbital or cycle time in Finnish, is the time it takes for an object to complete one revolution or cycle relative to a reference point. The term is used in different fields, most notably astronomy to describe orbital periods, and in engineering and production to denote a cycle time or throughput interval. The concept is always measured as a duration from one completing event to the next identical event.

In astronomy, kiertoaika refers to the orbital period of a body around a central body, such as a planet around a star or a moon around a planet. The duration depends on the distance between the bodies and the masses involved, as described by Kepler’s laws and Newtonian gravity. For example, Earth’s kiertoaika around the Sun is about one year, while the Moon’s kiertoaika around the Earth is roughly 27 days (sidereal) or 29.5 days (synodic). The term distinguishes orbital motion from rotation about a body’s own axis.

In engineering and production, kiertoaika describes the cycle time—the time required to complete one cycle of a process, including processing, handling, and waiting periods. It is a key metric for capacity planning and efficiency analysis. Shorter kiertoaika generally enables higher output, but must be balanced with quality and safety considerations. In manufacturing, it is distinct from related measures such as lead time and throughput, and is often used to optimize workflows and scheduling.

Etymologically, kiertoaika comes from kiertää, “to revolve,” and aika, “time.” See also orbital period, synodic period, and cycle time.