Lunar Phase Calculator
Calculate the current moon phase, illumination, moon age, and moonrise/moonset times. Perfect for astronomy enthusiasts, stargazers, photographers, and anyone planning to observe the night sky.
What Are Lunar Phases?
Lunar phases are the different appearances of the Moon as seen from Earth over the course of a lunar month (approximately 29.53 days). The phases are caused by the changing relative positions of the Moon, Earth, and Sun. As the Moon orbits Earth, different portions of its illuminated half become visible to us.
The eight primary lunar phases are:
- New Moon: The Moon is between Earth and the Sun. The illuminated side faces away from us.
- Waxing Crescent: A sliver of the Moon becomes visible on the right side.
- First Quarter: Half of the Moon is illuminated (right side).
- Waxing Gibbous: More than half illuminated, growing toward full.
- Full Moon: The entire illuminated side faces Earth.
- Waning Gibbous: More than half illuminated, shrinking from full.
- Last Quarter: Half of the Moon is illuminated (left side).
- Waning Crescent: A sliver of the Moon remains visible on the left side.
How Does the Lunar Phase Calculator Work?
The calculator uses astronomical algorithms to determine the moon's phase:
Phase Angle: The angle between the Sun and Moon as seen from Earth.
Illumination: k = (1 + cos(θ)) / 2, where θ is the phase angle.
Moon Age: The time since the last new moon, measured in days.
Moonrise/Moonset: Calculated using the observer's latitude, longitude, and timezone.
The algorithm uses the Julian Day Number to calculate the moon's position, phase angle, and illumination. It then determines the phase name based on the illumination percentage and the moon's position relative to the sun.
Why Use This Lunar Phase Calculator?
- Accurate Calculations: Uses standard astronomical algorithms for precise results.
- Visual Moon Display: A realistic moon visualization shows the current phase.
- Moonrise & Moonset: Get rise and set times for your location.
- Next Events: Find the dates of the next new moon and full moon.
- Free & Private: No registration, no data storage.
Understanding Moon Illumination
- 0%: New Moon — the Moon is completely dark.
- 1-49%: Waxing Crescent — the Moon is growing brighter.
- 50%: First Quarter — exactly half illuminated.
- 51-99%: Waxing Gibbous — more than half illuminated.
- 100%: Full Moon — completely illuminated.
❓ Lunar Phase Calculator FAQ
What is a lunar phase?
A lunar phase is the appearance of the Moon's illuminated portion as seen from Earth. The phases change over a 29.53-day lunar cycle as the Moon orbits Earth.
How many lunar phases are there?
There are eight primary phases: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent.
What is the Moon's illumination?
Illumination is the percentage of the Moon's visible surface that is lit by the Sun. It ranges from 0% (New Moon) to 100% (Full Moon).
What is Moon age?
Moon age is the number of days since the last New Moon. It ranges from 0 to 29.53 days over the lunar cycle.
How long is a lunar cycle?
A lunar cycle (synodic month) is approximately 29.53 days — the time between two consecutive New Moons.
What is a Blue Moon?
A Blue Moon is the second Full Moon in a calendar month. It occurs about once every 2.7 years.
What is a Supermoon?
A Supermoon occurs when a Full Moon coincides with the Moon's closest approach to Earth (perigee). The Moon appears larger and brighter than usual.
What is a Blood Moon?
A Blood Moon is a total lunar eclipse where the Moon appears reddish due to sunlight scattering through Earth's atmosphere.
How do I calculate moonrise and moonset times?
Moonrise and moonset times depend on your latitude, longitude, and timezone. The calculator computes these using astronomical algorithms.
Does the Moon rise and set at the same time every day?
No. The Moon rises and sets about 50 minutes later each day, which is why the phases change over time.
What is the difference between a Full Moon and a New Moon?
A Full Moon occurs when the Earth is between the Sun and the Moon, and the entire illuminated side faces us. A New Moon occurs when the Moon is between Earth and the Sun, and the illuminated side faces away.
What is a Harvest Moon?
The Harvest Moon is the Full Moon nearest to the autumnal equinox (around September). It rises earlier than usual, providing extra light for farmers.
What is a Hunter's Moon?
The Hunter's Moon is the Full Moon following the Harvest Moon, typically in October. It has similar characteristics to the Harvest Moon.
What is a lunar eclipse?
A lunar eclipse occurs when the Earth passes between the Sun and the Moon, casting a shadow on the Moon. It can only happen during a Full Moon.
What is a solar eclipse?
A solar eclipse occurs when the Moon passes between the Sun and Earth, casting a shadow on Earth. It can only happen during a New Moon.
How does the Moon affect tides?
The Moon's gravitational pull causes ocean tides. Spring tides (higher and lower than normal) occur during New and Full Moons, while neap tides occur during First and Last Quarters.
Is this calculator accurate for any location?
Yes. The calculator uses your latitude, longitude, and timezone to provide accurate moonrise and moonset times for your specific location.