Moon Phase Calculator
NewFind the approximate moon phase for any date using a standard astronomical approximation — new moon, quarters, gibbous, and full moon, with a visual phase indicator.
Frequently Asked Questions
How accurate is this calculation?
It uses Conway's Moon Phase Algorithm, a widely-used astronomical approximation based on the moon's ~29.53-day synodic month — it's typically accurate to within about a day, which is precise enough for reference purposes but not for professional astronomy.
Why does the phase not exactly match what I see in the sky tonight?
Small discrepancies (usually under a day) can occur because the moon's actual orbital speed varies slightly throughout its cycle, while this calculation assumes a constant average cycle length — for exact-to-the-hour data, a full ephemeris-based astronomical calculation is needed.
What do the 8 phase names mean in order?
Starting from New Moon (fully dark) and going through waxing (growing) phases to Full Moon (fully lit), then through waning (shrinking) phases back to New Moon: New Moon → Waxing Crescent → First Quarter → Waxing Gibbous → Full Moon → Waning Gibbous → Last Quarter → Waning Crescent.
Does this account for my location on Earth?
No — the phase of the moon (how much of it is illuminated as seen from Earth) is the same worldwide at any given moment; only the exact rise/set times and visible orientation change by location, not the phase itself.