The Eight Moon Phases, in the Order You See Them

The Moon does not change shape. Sunlight always illuminates half of it; as the Moon travels around Earth, your viewing angle changes and you see a different portion of that lit half. NASA lists eight phases in a cycle that repeats from new Moon to new Moon in about 29.5 days.

The order to remember

The sequence is new Moon, waxing crescent, first quarter, waxing gibbous, full Moon, waning gibbous, third quarter, and waning crescent. “Waxing” means the visible bright portion is growing. “Waning” means it is shrinking. “Quarter” refers to the Moon's position in its orbit, not to seeing one-quarter of the lunar disk lit.

At new Moon, the Moon is in the same part of the sky as the Sun from our viewpoint, so its sunlit side faces away from us. A waxing crescent follows. First quarter shows roughly half of the visible disk lit, then waxing gibbous grows toward full Moon. At full Moon, the Moon is opposite the Sun as viewed from Earth and the near side is brightly lit.

After full Moon, the sequence reverses: waning gibbous, third quarter, and waning crescent lead back to new Moon. The exact appearance depends on where you are observing, but the orbital cause is the same.

Why the same side faces us

NASA Space Place explains that the Moon rotates on its axis at the same rate that it orbits Earth. That synchronized motion is why the same side generally faces us. It is sometimes called the “dark side,” but that phrase is misleading: the far side receives sunlight too. “Far side” describes what faces away from Earth, not a side that is permanently dark.

The Moon's orbit takes about 27.3 days relative to the stars, while the familiar phase cycle takes about 29.5 days because Earth and Moon are both moving around the Sun. NASA's phase guide also gives the Moon's average distance as 238,855 miles (384,399 kilometers).

Make a small observation log and name what you see

You can learn the order without special equipment. Once every few evenings, record the date, the approximate shape of the bright part, and whether it is growing or shrinking. Add the time and direction only if they help you find the Moon again. A simple line might read: “Date — broad bright side — waxing gibbous.”

After several entries, compare your notes with a current lunar calendar. A weather cloud or a low horizon can leave a blank; that is a missing observation, not a missing phase. The cycle is continuous even when you cannot see it.

When you see about half the disk lit, ask which half of the cycle you are in. If the bright portion is growing, it is first quarter; if it is shrinking, it is third quarter. A nearly full disk is gibbous, and a narrow curve is crescent. The name tells you both the amount and the direction of change. Keep the eight names in order, then use the two verbs—waxing and waning—to orient yourself.