Calculator
Enter any date to see the moon's phase and how far it is through its roughly 29.5-day cycle.
The moon's cycle from one new moon to the next averages 29.53 days (the synodic month), though the exact length varies slightly from cycle to cycle due to the moon's elliptical orbit. This calculator counts days since a known reference new moon and divides by that average, which puts it within about a day of an official almanac for most dates — precise enough for planning, but not a substitute for a professional ephemeris if you need second-level accuracy for something like astronomical research.
New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent — each covering roughly one eighth of the cycle.
Related
Sunrise and sunset times for any date and location.
How many hours of daylight a given date has.
Build a live countdown to any date, including the next full moon.