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Moon Phase Calculator
Identify the current lunar phase, age of the moon, and its percentage of illumination.
Current Phase
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Moon Age
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Illumination
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The Lunar Cycle Explained
The moon goes through eight distinct phases as it orbits Earth every 29.5 days. These phases are determined by the moon's position relative to the Earth and the Sun, which dictates how much of the moon's surface is illuminated from our perspective.
The Eight Phases
- New Moon: The moon is between Earth and Sun.
- Waxing Crescent: A small sliver grows visible.
- First Quarter: Half of the moon is lit.
- Waxing Gibbous: Most of the moon is lit.
- Full Moon: The entire face is illuminated.
- Waning Gibbous: The illuminated area shrinks.
- Last Quarter: The opposite half is lit.
- Waning Crescent: A final sliver before the new cycle.
Frequently Asked Questions (FAQ)
Why do we always see the same side of the moon?
This is due to "tidal locking." The moon rotates on its axis in exactly the same amount of time it takes to orbit Earth.
How long is a lunar month?
A synodic month (the time between two new moons) is approximately 29.53 days.
Is the illumination percentage the same everywhere on Earth?
Yes. The phase of the moon is determined by the geometry of the Sun, Earth, and Moon, so everyone on Earth sees the same phase on the same night.