Two to five a year
Every calendar year has at least two solar eclipses somewhere on Earth, and some years have as many as five. Years with five are very rare; two or three is typical.
Over the long run, astronomers count about 238 solar eclipses per century. Of those, about:
| Type | Share of all solar eclipses |
|---|---|
| Partial | About 35% |
| Annular | About 33% |
| Total | About 27% |
| Hybrid (total in some places, annular in others) | About 5% |
These are rounded figures from long-term catalogs of eclipses compiled at NASA. They mean that total and annular eclipses each happen roughly every year or two, somewhere in the world.
Why eclipses come in seasons
A solar eclipse needs a new moon, and there is a new moon every 29.5 days. But the Moon’s orbit is tilted about 5 degrees from Earth’s, so the Moon usually slips above or below the Sun as seen from Earth.
The Moon’s orbit crosses the plane of Earth’s orbit at two points called nodes. An eclipse is possible only when the Sun is near one of the nodes at new moon. The Sun passes a node about every 173 days, so there are two eclipse seasons a year, each lasting a little over a month. Every eclipse season has at least one solar eclipse and sometimes two.
The line of nodes also turns slowly, so eclipse seasons arrive about 19 days earlier each year. That is why eclipses do not stay in the same months.
The saros cycle
Ancient astronomers noticed that eclipses repeat in a pattern. After a period of about 18 years, 11 days and 8 hours, called a saros, the Sun, Moon and nodes return to almost the same arrangement, and a very similar eclipse happens again.
The extra 8 hours matter: in that time Earth turns about a third of the way around, so the repeated eclipse falls roughly 120 degrees of longitude farther west. After three saros periods, about 54 years and a month, a similar eclipse returns to roughly the same longitude.
Many saros series run at the same time, each producing one eclipse every 18 years for more than a thousand years.
How rare is one in your town?
Here is where the numbers drop sharply. A partial solar eclipse is fairly common: most places see one every few years, because the Moon’s outer shadow covers a huge area.
The central path of a total eclipse, though, is usually only a hundred to a couple of hundred kilometers wide. On average, any particular spot on Earth sees a total solar eclipse roughly once every 375 years. That is only an average. Some places wait more than a thousand years, while a few lucky spots see two within a couple of decades.
Annular eclipses have similar odds, since they also need you to be inside a narrow central path.
Plan around the paths
Because the chance of totality coming to you is low, many people travel to it. Eclipse paths are predicted many years in advance, and the eclipses page lists upcoming solar and lunar eclipses with where they can be seen. To understand what you will see in each case, read about what a solar eclipse is and the total solar eclipse.
Lunar eclipses are easier to catch
Lunar eclipses happen at a similar overall rate, but each one can be seen from the entire night side of Earth, more than half the planet. That makes a lunar eclipse much easier to see from home than a total solar eclipse. You can check the current moon phases to see when the next full moon is.