Moon Phase Calculator

Find the approximate moon phase for any date using a well-established astronomical approximation — no location needed.

Unlike sunrise and sunset, which depend heavily on where you are on Earth, the moon's phase is the same everywhere in the world on any given date — the moon doesn't wax and wane differently for different observers, only its visibility above the horizon changes with the time of night and your location, which makes moon phase one of the few astronomical facts that can be calculated purely from a date, without needing any location input at all.

The calculation used here is a well-established approximation technique — sometimes credited to the mathematician John Conway — that estimates the moon's phase using the date alone, accurate to within roughly a day, which is more than sufficient for general reference use even though it's not the kind of precision an astronomer tracking exact lunar timing would rely on for professional work.

Enter any date, and this tool returns the approximate moon phase — new, full, or one of the waxing or waning stages in between. It's useful for anyone curious about lunar timing for a specific date, whether that's planning around a full moon for photography, checking a birth date's moon phase out of curiosity, or just satisfying general interest in where the moon cycle stood on a particular day.

1. Pick any date.
2. Press Find moon phase.
3. See the approximate lunar phase for that date.