Moon phase calculator
Pick a date to see the moon phase and how illuminated it is.
Moon phase calculator
Find the moon phase and rough illumination for any date — new moon, waxing crescent, first quarter, full moon and so on. Useful for photography, gardening, fishing and stargazing.
How it works
The Moon cycles through its phases over a synodic month of about 29.53 days. The calculator measures the days since a known new moon and maps the position in the cycle to one of the eight phases, plus an approximate percentage of the disc that’s lit. It’s an estimate, accurate to about a day.
Frequently asked questions
What is a synodic month? The ~29.53-day cycle from one new moon to the next.
How accurate is it? Within roughly a day — fine for planning, not for precise astronomy.