In this article
Why the Moon's distance changes
The Moon does not circle Earth in a perfect circle. Its orbit is an ellipse, so the distance swings between roughly 356,000 and 407,000 kilometres. The nearest point is called perigee and the farthest apogee, and the exact figures differ a little from one month to the next.
A full moon can fall anywhere along that path. When it lands near perigee it is a little larger and brighter than usual. When it lands near apogee it is a little smaller and dimmer. The table shows the distance for each one in your local time zone.
Where the word supermoon comes from
"Supermoon" is a popular term, coined by the astrologer Richard Nolle in 1979. Astronomers prefer the plainer phrase perigee full moon. There is no single official definition: Nolle used a full moon within 90 percent of the closest approach, while others set a fixed distance.
On this site the table uses a distance of about 362,500 kilometres. Full moons closer than that are labelled supermoons, and the most distant ones are labelled micromoons. A different cut-off would move a few of the borderline cases.
The two labels
Each type has its own page with the practical details.
Can you really see the difference?
A supermoon can look up to about 14 percent wider and roughly 30 percent brighter than a micromoon. Alone in the sky, that is very hard to notice, because we have nothing to compare it with. Side-by-side photographs taken months apart show it clearly.
The huge orange Moon near the horizon is another matter. That is the Moon illusion, a trick of perception that happens at every full moon, not an effect of distance.
Tides, worries and folklore
Near perigee the Moon's pull is slightly stronger, so spring tides can run a few centimetres higher. That is not dangerous by itself. There is no scientific evidence linking supermoons to earthquakes, storms or other disasters, so you can enjoy them without worry.
Astrology reads a full moon as a time of culmination, and a supermoon as a stronger version of it. That is a tradition and a matter of taste. For the monthly rhythm, see the Moon phases hub, and for shadows crossing the Moon, the eclipses hub.
Questions people ask
How often is there a supermoon?
Several times a year, often in a row of two to four. How many depends on the cut-off distance, which is why different sources give different counts.
Is a supermoon dangerous?
No. It can raise some tides by a few centimetres, but there is no evidence of any link to earthquakes or disasters.
Does the table change with my location?
The distance does not, since it is measured from the centre of Earth. The date and time are shown in your local time zone.