A full moon happens about once every 29.5 days, so you see one roughly once a month (about 12–13 times a year).

Here’s the quick scoop, in a slightly more narrative style.

What “how often” really means

  • The Moon’s phase cycle (new → full → new) takes about 29.5 days, called a synodic month.
  • That means from one full moon to the next is also about 29.5 days.
  • Because our calendar months are 28–31 days, most months get one full moon, some very occasionally get two.

So in a typical calendar year, you’ll see 12 full moons, but some years squeeze in a 13th.

Fun timing quirks

  • If a full moon falls in the first couple of days of a month, the next one can slip in before that month ends, giving you two full moons that month.
  • That extra full moon is often called a “blue moon” , which happens on average every 2–3 years.
  • Astronomers still say there’s only one exact full-moon moment, but to our eyes the Moon looks “full” for about three nights in a row.

Simple way to think of it

If you spot a bright, round full moon tonight, you can expect the next one in just under a month—close enough that “about once a month” is a good everyday answer.

TL;DR: A full moon occurs roughly every 29.5 days, which works out to about one full moon per month, or 12–13 full moons each year.