A waxing moon is a Moon whose lit part grows each night, from new moon to full moon, and a waning moon is one whose lit part shrinks, from full moon back to new moon. As seen from the Northern Hemisphere, a waxing moon is lit on the right and a waning moon is lit on the left.
Key facts
- Waxing: lit part grows, from new moon to full moon. Waning: lit part shrinks, from full moon to new moon.
- Northern Hemisphere: lit on the right means waxing, lit on the left means waning. Southern Hemisphere: the reverse.
- Time-of-day rule for anywhere on Earth: a Moon already up at sunset is waxing; a Moon still up at sunrise is waning.
- Each half of the cycle lasts about 14.8 days.
What do waxing and waning mean?
Waxing means growing and waning means shrinking: the words describe whether the lit part of the Moon is getting larger or smaller from one night to the next.
The 29.5-day cycle of the phases of the moon splits into two halves of about 14.8 days each, at the new moon and the full moon.
- Waxing phases: the waxing crescent, the first quarter and the waxing gibbous. The Moon is east of the Sun in the sky and moving away from it.
- Waning phases: the waning gibbous, the last quarter and the waning crescent. The Moon is west of the Sun in the sky and moving back toward it.
Both words come from Old English. Wax comes from Old English weaxan, “to grow,” and wane comes from wanian, “to diminish.” The two have been paired to describe the Moon since early Middle English.
How do you tell if the Moon is waxing or waning from the lit side?
As seen from the Northern Hemisphere, a Moon lit on the right is waxing and a Moon lit on the left is waning; in the Southern Hemisphere, lit on the left is waxing.
The lit side always faces the Sun. A waxing moon sits east of the Sun, so the Sun lights it from the west. To an observer in the Northern Hemisphere facing south toward the Moon, west is on the right. In the Southern Hemisphere, observers face north toward the Moon, so west is on the left and the pattern flips.
The DOC memory aid
In the Northern Hemisphere, the Moon’s shapes in order spell D, O, C. A waxing moon lit on the right looks like a D, the full moon looks like an O, and a waning moon lit on the left looks like a C. In the Southern Hemisphere the order runs C, O, D.
French speakers use a related trick: “la Lune est menteuse,” or “the Moon is a liar.” A D-shaped Moon is actually croissant (growing), and a C-shaped Moon is actually décroissant (shrinking), so each letter points to the wrong word. The saying works in the Northern Hemisphere only.
The reason the whole view turns over south of the equator is covered in why the moon looks upside down in the southern hemisphere.
How do you tell if the Moon is waxing or waning by the time of day?
A Moon that is already in the sky at sunset is waxing, and a Moon that is still in the sky at sunrise is waning; this rule works in both hemispheres.
A waxing moon rises during the day, after the Sun, and is up in the evening. A waning moon rises during the night, after sunset, and is still up in the morning. The full moon is the only phase that is up at both sunset and sunrise.
- Afternoon or evening Moon: waxing. Look for it after sunset, or east of the Sun during the afternoon.
- Late-night or morning Moon: waning. Look for it before dawn, or west of the Sun during the morning.
- Moon rising in the east at sunset: full or very close to full.
How do you tell waxing from waning near the equator?
Near the equator the left-right rule breaks down, because the crescent often lies almost flat, with its horns pointing up like a boat; use the direction of the lit edge or the time of day instead.
Close to the equator, the terminator often appears horizontal in the evening and morning. A crescent seen there can look like a bowl or a smile, with no clear left or right side. The lit edge still points toward the Sun:
- In the evening, a crescent with its lit edge down toward the western horizon, where the Sun has just set, is waxing.
- Before dawn, a crescent with its lit edge down toward the eastern horizon, where the Sun is about to rise, is waning.
Why can a telescope give the wrong answer?
A telescope can give the wrong answer because many telescopes turn the image upside down or show it as a mirror image, which moves the lit side.
A reflecting telescope rotates the view by 180°, so a waxing moon lit on the right appears lit on the left in the eyepiece. A refractor used with a star diagonal shows a mirror image, which also swaps left and right. Binoculars show the Moon the right way round. Before applying the left-right rule, check which side is lit with the naked eye.
Waxing vs waning: comparison table
The table below sets the waxing and waning halves of the cycle side by side, with the Northern and Southern Hemisphere views.
| Waxing moon | Waning moon | |
|---|---|---|
| Lit part | Grows each night | Shrinks each night |
| Runs from | New moon to full moon | Full moon to new moon |
| Phases | Waxing crescent, first quarter, waxing gibbous | Waning gibbous, last quarter, waning crescent |
| Lit side, Northern Hemisphere | Right | Left |
| Lit side, Southern Hemisphere | Left | Right |
| Position in the sky | East of the Sun | West of the Sun |
| Rises | Between sunrise and sunset | Between sunset and sunrise |
| Best seen | Evening | Late night and morning |
| In daylight | Afternoon | Morning |
| Lit edge points toward | The setting Sun, in the west | The rising Sun, in the east |
| Typical length | About 14.8 days | About 14.8 days |
Is the Moon waxing or waning right now?
The live card below shows whether the Moon is waxing or waning at this moment, with its illumination and age.
A waxing moon turns into a waning moon at the full moon, and the next full moon is on . A waning moon starts waxing again after the new moon, and the next new moon is on . The moon phase today page shows the same information together with the next moonrise.