New moon
Typical illumination
The sunlit face is turned away from Earth, so the disc looks dark in the night sky.
The eight names
Moon Phases
Moon phases on this page are the usual U.S. names for the Moon's place in the cycle. Each disc is a Northern Hemisphere view: waxing light grows on the right. The percent is typical for that name in this model, not a live reading. For tonight's figure, open the home page. For one calendar date, use the moon phase calculator.
Waxing crescent
Typical illumination
A thin sliver is growing on the right as seen from the Northern Hemisphere.
First quarter
Typical illumination
About half the near side is lit. In this Northern Hemisphere view, the right half is the bright side.
Waxing gibbous
Typical illumination
More than half the disc is lit, and the bright portion is still growing toward full.
Full moon
Typical illumination
The near side is almost fully sunlit, so the disc looks round and bright.
Waning gibbous
Typical illumination
The disc is still mostly lit, and the dark portion is growing from the right.
Last quarter
Typical illumination
About half the near side is lit. In this Northern Hemisphere view, the left half is the bright side.
Waning crescent
Typical illumination
A thinning sliver remains on the left as seen from the Northern Hemisphere.
These figures are for learning and curiosity. They are not an observatory ephemeris, and they are not a guide for navigation.
How the names are assigned
The calculator uses the Moon's elongation from the Sun. New is near 0°, first quarter near 90°, full near 180°, and last quarter near 270°. The in-between names are the crescents and the gibbous phases. Illumination is (1 + cos i) / 2, so a quarter day is not locked to exactly 50 percent.
A mean synodic month is 29.530588853 days. People sometimes treat the names as a mood clock; that is folklore, not a finding from these figures. Tonight's live disc is on the moon phase page. Dates for every full and new moon in a year are on the full moon dates list.
Questions
Why are there eight names instead of four?
New, first quarter, full, and last quarter are the principal phases. The four names in between describe whether the lit portion is a crescent or more than half, and whether it is growing or shrinking.
Does waxing always mean the right side is lit?
On this site, yes, because the disc is a Northern Hemisphere view. From much of the Southern Hemisphere the waxing crescent sits on the other side. The page does not flip the picture by city.
Is this a horoscope?
No. There is no natal chart and no claim that a phase changes sleep or luck. The names stop at geometry.
Where is tonight's moon?
On the home page. This page is a map of the names. The calculator for any date from 1900 to 2100 is the moon phase calculator.