๐ŸŒ™ Moon Phase Calculator

See what phase the Moon is in on any date (today, your birthday, or ten years from now), plus when the next new, quarter, and full moons land.

๐ŸŒ— This uses the Moon's average 29.53-day cycle, the same method most online moon calendars use. Because the Moon's orbit isn't a perfect circle, real phase times can drift by up to about half a day from this estimate, close enough for planning a moonlit walk, not precise enough for eclipse chasing.

๐Ÿ“… Pick a Date

Works for any date, past or future.

๐ŸŒŒ Moon Phase Results

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Illumination: Moon age:

Next four major phases

๐ŸŒ— What each phase means

"Waxing" means the lit portion is growing night to night; "waning" means it's shrinking. "Gibbous" just means more than half lit but not full.

๐ŸŒ‘
New Moon
The Moon sits between Earth and the Sun, so its lit side faces away from us. It's invisible, or nearly so, in the night sky, and marks the start of the cycle.
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Waxing Crescent
A thin sliver of light appears and grows a little bigger each night as the Moon moves away from the Sun's glare.
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First Quarter
Exactly half the face we see is lit. It's called "first quarter" because the Moon has completed one quarter of its trip around Earth, not because a quarter of it is lit.
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Waxing Gibbous
More than half lit and still growing night by night, closing in on full.
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Full Moon
The Moon is directly opposite the Sun from Earth, so the entire face is lit. The brightest and most familiar phase, the midpoint of the cycle.
๐ŸŒ–
Waning Gibbous
Still more than half lit, but now shrinking each night on the way back down after full.
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Last Quarter
Half lit again, on the opposite side from First Quarter, three-quarters of the way through the cycle. Also called "Third Quarter."
๐ŸŒ˜
Waning Crescent
A thin, shrinking sliver just before the Moon disappears into the next New Moon and the cycle starts over.

Formula

Age = (Days since 6 Jan 2000 new moon) mod 29.53
Age = how many days into the current 29.53-day lunar cycle (0 = new moon)
Illumination โ‰ˆ 50 ร— (1 โˆ’ cos(2ฯ€ ร— Age รท 29.53))

The Moon takes about 29.53 days (a "synodic month") to cycle from one new moon to the next, which is slightly longer than its actual 27.3-day orbit around Earth because Earth itself keeps moving around the Sun in the meantime.