Current Moon Phase Today
See today's moon phase, illumination, and age in real time.
How It Works
The page loads your device's current date and time, converts it to a Julian Day Number, then applies the synodic month formula to calculate where the Moon sits in its current cycle. The result updates each time you load or refresh the page, so you always see today's phase.
Formula
The Eight Named Moon Phases
The lunar cycle is divided into eight phases based on the fraction of the Moon's disc that appears illuminated from Earth:
- New Moon (0%): Moon is between Earth and Sun; disc is dark.
- Waxing Crescent (1–49%): Right side lit and growing. Visible in the western sky after sunset.
- First Quarter (50%): Right half lit. Rises around noon, sets around midnight.
- Waxing Gibbous (51–99%): More than half lit and still growing toward full.
- Full Moon (100%): Entire disc illuminated. Rises at sunset, sets at sunrise.
- Waning Gibbous (99–51%): Past full, left side now leading. Rises after sunset.
- Last Quarter (50%): Left half lit. Rises around midnight, sets around noon.
- Waning Crescent (49–1%): Shrinking sliver on the left side. Visible just before sunrise.
Why the Moon Appears to Change Shape
The Moon does not emit its own light — it reflects sunlight. As the Moon orbits Earth over 29.53 days (the synodic month), the angle between the Sun, Earth, and Moon changes, altering how much of the illuminated hemisphere we can see. At new moon, the lit side faces away from us entirely. At full moon, the lit side faces us completely. The shape we see (the phase) is simply a geometric consequence of orbital geometry.
Cultural and Practical Significance
Moon phases have guided agriculture, fishing, navigation, and religious calendars for thousands of years. Many cultures plant by the moon (sowing above-ground crops during waxing phases, root crops during waning phases). Tidal strength peaks at new and full moon when gravitational alignment is greatest. Many religious calendars — Islamic, Hebrew, Hindu — are lunisolar, tying months to the new or full moon.
Frequently Asked Questions
What is the moon phase today?
This tool computes today's moon phase automatically from your device's date. It shows the phase name, illumination percentage, moon age in days, and a visual progress bar through the 29.53-day cycle.
How often does the moon phase change?
The moon phase changes continuously — it is not a discrete step but a smooth progression. The complete cycle from new moon back to new moon takes exactly 29.53059 days (the synodic month). The named phases are convenient labels for eight segments of this continuous cycle.
Is the moon phase the same everywhere on Earth?
Yes — the phase (what fraction is lit) is the same worldwide at any given moment. However, the moon appears higher or lower in the sky depending on your latitude, and the orientation of the crescent may look different in the Northern vs. Southern Hemisphere (it appears "upside down" in the Southern Hemisphere).
What is the difference between a waxing and waning moon?
Waxing means the illuminated portion is growing (new moon toward full moon). Waning means it is shrinking (full moon back toward new moon). Crescent refers to less than half lit; gibbous means more than half lit.