Moon Phase Calculator
Find the moon phase for any date. This calculator uses the synodic period (29.53059 days) from a known new moon reference (January 6, 2000) to determine the current phase, illumination percentage, and days into the lunar cycle. The 8 moon phases are: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent.
Moon Phase Calculator
Find the moon phase for any date. Shows phase name, illumination percentage, and next full/new moon dates.
First Quarter
10.0 days into the lunar cycle
Next Full Moon 🌕
Thursday, April 2, 2026
Next New Moon 🌑
Friday, April 17, 2026
Frequently Asked Questions
What are the 8 moon phases in order?
The 8 moon phases in order are: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, Waning Crescent. After Waning Crescent, the cycle returns to New Moon. Each phase lasts approximately 3.7 days.
How long is one lunar cycle?
One complete lunar cycle (synodic period) takes 29.53059 days — approximately 29 days, 12 hours, 44 minutes, and 3 seconds. This is the time from one new moon to the next. The sidereal period (time relative to distant stars) is shorter at 27.32 days.
What is the difference between a waxing and waning moon?
A waxing moon is growing in illumination (from new moon to full moon). A waning moon is decreasing in illumination (from full moon back to new moon). 'Wax' comes from Old English meaning 'to grow'; 'wane' means 'to decrease'.
When is the next full moon?
Use the calculator above to find the next full moon from any date. Full moons occur approximately every 29.5 days. The exact date varies because the lunar cycle doesn't align perfectly with calendar months.
How is moon phase calculated?
Moon phase is calculated by measuring the elapsed time since a known new moon reference date (January 6, 2000, 18:14 UTC), then finding the position within the 29.53-day synodic period. The cycle is divided into 8 equal segments, and the current position determines the phase name.
What is a supermoon?
A supermoon occurs when a full moon coincides with the moon's closest approach to Earth (perigee). Supermoons appear up to 14% larger and 30% brighter than a typical full moon. The moon's orbit is elliptical, so its distance from Earth varies between approximately 356,500 km (perigee) and 406,700 km (apogee).
Why does the full moon affect fishing and hunting?
Many anglers and hunters plan activities around moon phases. The theory is that animal activity (feeding, spawning) follows tidal rhythms influenced by lunar gravity. The full and new moon create the strongest gravitational pull (spring tides), which may correlate with increased fish and wildlife activity near water.
What is a blue moon?
The modern definition of a blue moon is the second full moon in a single calendar month. Since the lunar cycle is ~29.5 days and months have 28–31 days, a second full moon in one month occurs roughly once every 2.5 years — hence 'once in a blue moon.' The original definition was the third full moon in a season with four full moons.
About the Moon Phase Calculator
About This Calculator
The moon phase calculator determines the current phase of the Moon for any given date using the synodic period and a known new moon reference date. It also calculates the illumination percentage and finds the next full moon and new moon dates.
The 8 Moon Phases
| Phase | Emoji | Approx. Day | Illumination |
|---|---|---|---|
| New Moon | 🌑 | 0 | 0% |
| Waxing Crescent | 🌒 | 3.7 | 1–49% |
| First Quarter | 🌓 | 7.4 | ~50% |
| Waxing Gibbous | 🌔 | 11.1 | 51–99% |
| Full Moon | 🌕 | 14.8 | 100% |
| Waning Gibbous | 🌖 | 18.5 | 99–51% |
| Last Quarter | 🌗 | 22.1 | ~50% |
| Waning Crescent | 🌘 | 25.8 | 49–1% |
Synodic Period
The Moon's synodic period is the time between two consecutive new moons: 29.53059 days. This is longer than the sidereal period (27.32 days) because the Earth is simultaneously orbiting the Sun, so the Moon needs extra time to "catch up" to reach the same phase relative to the Sun.
One complete lunar cycle takes ~29 days 12 hours 44 minutes 3 seconds.
How the Phase Is Calculated
This calculator uses a known new moon reference point (January 6, 2000, 18:14 UTC) and counts elapsed days modulo the synodic period:
- Calculate the time elapsed since the reference new moon
- Compute the position within the current synodic cycle (elapsed time mod 29.53059 days)
- Divide the cycle into 8 equal segments of ~3.69 days each
- Determine which segment the current date falls in to get the phase name
Illumination Percentage
Illumination = (1 − cos(2π × phaseAge / synodicPeriod)) / 2 × 100%
This formula gives 0% at new moon (phase age = 0), 100% at full moon (phase age = 14.77 days), and 50% at the quarter moons. It provides a smooth approximation of the Moon's illuminated fraction.
Practical Uses of Moon Phase Information
- Astronomy — Full moon creates light pollution; new moon is ideal for deep-sky observing
- Photography — Landscape photographers plan moonlit shoots around full moon
- Fishing and hunting — Many anglers and hunters use moon phases to predict animal activity
- Gardening — Biodynamic farming uses moon phases for planting cycles
- Cultural/Religious — Many calendars (Islamic, Hebrew, Hindu) are lunar or lunisolar
- Navigation — Sailors historically used the full moon for nighttime navigation