A full lunar cycle (from one new moon to the next) lasts about 29.5 days on average.

Quick Scoop: How long is the lunar cycle?

  • The lunar cycle (also called a synodic month or lunation) is the time it takes the Moon to go through all its phases and return to the same phase, usually new moon to new moon.
  • On average, this is about 29.53 days — often rounded to 29.5 days.
  • This is why many traditional lunar calendars use months of 29–30 days.

Why not a neat 30 days?

  • The Moon orbits Earth in about 27.3 days (a sidereal month), but during that time Earth also moves along its orbit around the Sun.
  • Because Earth has shifted position, the Moon has to travel a bit farther to line up with the Sun in the same way again (new moon to new moon), which stretches the cycle to about 29.5 days.

Mini note: different “months” of the Moon

Astronomers sometimes talk about several lunar “months”:

  • Synodic month (phases cycle): ~29.53 days — this is what most people mean by “lunar cycle”.
  • Sidereal month (one orbit relative to the stars): ~27.3 days.
  • Anomalistic month (perigee to perigee, closest approach): ~27.55 days.

In everyday terms

If you see a new moon tonight, you’ll see the next new moon in just under 30 days , roughly four weeks plus a day and a half.

Information gathered from public forums or data available on the internet and portrayed here.