Enter a date, and the tool calculates the moon's phase, illumination percentage, and lunar age, with a matching emoji icon.
It uses the average synodic month (29.53 days) from a known new moon, so it is accurate to within roughly a day — great for a quick reference, planning or curiosity.
New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter and Waning Crescent — the full cycle repeats about every 29.5 days.
It is the fraction of the Moon's visible disc lit by the Sun — 0% at new moon, 100% at full moon.