How long is one cycle of moon phases?

What is the average (in days) between phases?

One cycle of the moon phases last for almost around 29 and a half days or 29.5 days.

There are four phases of the moon.

The average number of days between 4 intermediate phases of moon is approximately 7.4 days, however between full, waning/waxing gibbous, waning / waxing crescent, and new moon is around 3.5 days.