Lunar phase basics
A moon phase is the shape of the lit part of the Moon as seen from Earth, set by the angle between the Sun and Moon. The cycle runs from new Moon through waxing crescent, first quarter, waxing gibbous, full Moon, and back through the waning phases over about 29.5 days.
Phase calculation method
This calculator measures the angular distance between the Sun and Moon for the date you choose, then maps it to one of the eight phases and an illumination percentage. The numbers come from Swiss Ephemeris astronomy, so they match what you see in the sky.
Phase and Moon sign together
Alongside the phase, the tool shows the zodiac sign and degree the Moon occupies that day. The phase describes the light; the sign describes the Moon position in the zodiac. Together they give a fuller picture of the lunar day.
Date lookup and next steps
Pick any date to see its phase, illumination, and Moon sign, past, present, or future. The phase is a description of the sky, not a forecast. For your personal Moon, try the Moon sign calculator.