A full Moon happens about once every 29.5 days, which works out to usually 12, and sometimes 13, full Moons in a year.

Quick Scoop 🌕

  • The Moon’s phase cycle (from one full Moon to the next) is called a synodic month and lasts about 29.5 days.
  • Because most calendar months are 30 or 31 days long, you normally see one full Moon per month.
  • Every couple of years there’s an extra, 13th full Moon in a year; this is when you can get a so‑called “blue Moon” (a second full Moon in one month or an extra one in a season).

Mini breakdown

  1. From one full Moon to the next: ~29.5 days.
  1. Typical number per year: 12 full Moons.
  1. Occasionally: 13 full Moons in a year (every ~2–3 years, giving a “blue Moon”).

So if you’re planning a moon‑watching night, you can think of a full Moon as showing up a bit less often than “once a month,” on a roughly 29½‑day rhythm.

TL;DR: A full Moon occurs roughly every 29.5 days, usually giving 12 full Moons per year, with an extra one (a blue Moon) every few years.

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