Moon Phase Calculator
Find out whether the Moon will be new, crescent, quarter, gibbous, or full on any date.
Moon phase
🌘 Waning Crescent
On 2026-08-12.
Illumination
0.8%
Share of the visible disc that is lit.
Lunar age
28.7 days
Days since the last new moon.
Days to next full moon
15.6
Days to next new moon
0.8
- Runs entirely in your browser
- No data is stored
- Free forever
What is this calculator?
The Moon runs on its own calendar, cycling from new to full and back roughly every 29.5 days. This calculator takes any date you pick and reports the phase name, how much of the disc is lit, how far into the cycle the Moon is, and how long you have to wait for the next full and new moon.
How does it work?
It counts the days since a known new moon in January 2000 and divides by the mean synodic month of 29.530588853 days. The fractional remainder is the lunar age, which maps directly to a phase name and to an illumination figure derived from the phase angle.
Frequently asked questions
How accurate is this?+
It uses the mean synodic month, so it is typically within a few hours of the true phase. The Moon's orbit is slightly irregular, which can shift exact moments a little.
What is lunar age?+
The number of days since the last new moon. Zero is new, about 14.8 days is full, and 29.5 days brings you back to new.
Does my time zone matter?+
Only near the exact moment of a phase change. Calculations are anchored at midday UTC on the date you choose.
Why isn't the full moon exactly 50% through the cycle?+
It very nearly is. Half of 29.53 days is 14.77 days, which is when illumination peaks.
What is a blue moon?+
A second full moon within one calendar month. It happens roughly every two and a half years because the lunar cycle is shorter than most months.
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