Thirteen is unlucky only by superstition. There's no evidence that the number brings bad luck, but the belief is old and widespread in Western countries, strong enough that some buildings skip a 13th floor and some airlines leave out row 13. Its origins are murky: the popular explanations, from the thirteen diners at the Last Supper to a Norse myth and the arrest of the Knights Templar, are good stories but none has been shown to be the source.

In many other places 13 is neutral, and in a few it's actually lucky. Here's what's known, what's guesswork, and how numerology reads the number.

The fear has a name

Fear of the number 13 is called triskaidekaphobia, from the Greek for "three", "and ten" and "fear". Fear of Friday the 13th has two even longer names: paraskevidekatriaphobia, from the Greek for Friday, and friggatriskaidekaphobia, after Frigg, the Norse goddess from whom Friday may take its name.

Most people who avoid 13 don't have a phobia in the clinical sense. They just prefer not to book a wedding on Friday the 13th, or feel a small flicker when the hotel gives them room 1313. That flicker is what superstition looks like in daily life.

Three origin stories, none proven

These are the explanations you'll see most often. Each has a grain of history in it, and each falls short as proof.

The Last Supper

Jesus and his twelve apostles made thirteen at the table, and Judas, the betrayer, is sometimes described as the thirteenth to sit down. That's the root of the folk belief that thirteen at dinner is bad luck, sometimes said to mean one guest will die within the year. The Gospels, though, don't count the seating order, and the superstition about thirteen at table is recorded much later than the events it explains.

Loki, the thirteenth guest

A popular retelling has twelve Norse gods feasting in Valhalla when Loki, the trickster, arrives as an uninvited thirteenth and engineers the death of the beloved god Baldr. The medieval sources tell Baldr's death differently, at a gathering where the gods amuse themselves throwing things at him, with no dinner party and no headcount of thirteen. The "thirteenth guest" version looks like a modern stitching together of separate stories.

The Knights Templar

On Friday, October 13, 1307, officers of King Philip IV of France arrested members of the Knights Templar across the country, the start of the order's destruction. The date is real. But the link to the Friday the 13th superstition only appears in modern retellings, and historians haven't found it in older sources.

How Friday the 13th became a thing

Friday and 13 were each considered unlucky on their own before anyone put them together. In parts of Christian Europe, Friday carried a shadow as the day of the crucifixion, and some sailors and travelers avoided starting a voyage on one.

The combination appears in the nineteenth century and became famous in the twentieth. A 1907 novel by the American financier Thomas W. Lawson, Friday, the Thirteenth, told of a broker who used the superstition to set off a panic on Wall Street. Some historians think the book helped make the phrase familiar. The horror film Friday the 13th, released in 1980, did the rest.

Where 13 is skipped, and where it's lucky

The superstition shows up in architecture and travel:

  • Buildings. Many hotels and towers skip from floor 12 to 14, or relabel 13 as 12A or 14. The floor still exists, of course.
  • Planes and hospitals. Some airlines leave out row 13, and some hospitals skip room 13.
  • Dinner parties. In the 1880s a group in New York called the Thirteen Club met to mock the superstition, sitting thirteen to a table, walking under ladders and spilling salt on purpose.

But 13 isn't unlucky everywhere:

  • In Italy, 13 has traditionally been a lucky number, and 17 is the unlucky one. Written in Roman numerals, XVII can be rearranged as VIXI, Latin for "I have lived", a phrase found on tombs.
  • In Jewish tradition, a boy becomes bar mitzvah at 13, and the rabbinic tradition counts thirteen attributes of God's mercy.
  • In China, the number to avoid is 4, not 13, because of how it sounds. Our guide to lucky numbers in Chinese culture explains why.

People also point to Apollo 13, launched at 13:13 Houston time in April 1970, which suffered an explosion on April 13. The crew got home safely. Coincidences like that are memorable precisely because we're already primed to notice 13.

13 in numerology and tarot

Numerology doesn't treat 13 as unlucky. Its digits add to 1 + 3 = 4, the number of work, structure and patient effort, explained on our life path 4 page. When 13 appears as a total just before the final reduction in your core numbers, some numerologists call it a karmic debt number, written 13/4 and read as a lesson about doing the work properly rather than looking for shortcuts. That's a call to steady effort, not a curse.

In tarot, card XIII is Death, which almost never means a literal death. Readers interpret it as an ending that makes room for something new: a job, a habit, a chapter. That's a reasonable way to look at 13 in general. It marks a turn, and turns can be good.

Astrology has its own thirteen controversy, too, over whether Ophiuchus should count as a 13th zodiac sign. The short answer is that the tropical zodiac used in Western astrology is tied to the seasons, not to the constellations.

Questions readers ask

Is Friday the 13th actually unlucky?

There's no good evidence that it is. The day is famous because the superstition is famous, and people remember the bad things that happen on it more than the ordinary ones.

Why do buildings skip the 13th floor?

Because some tenants, guests and buyers would rather not live or stay on a floor numbered 13, and skipping the number costs the building nothing. The 14th floor is, of course, the 13th floor by count.

Is 13 unlucky in the Bible?

The Bible gives 13 no special negative meaning. The association with the Last Supper is a later folk tradition. Our guide to the biblical meaning of numbers covers the numbers that do carry weight in scripture, such as 7, 12 and 40.

Is 13 a lucky number for anyone?

Yes. Plenty of people born on the 13th consider it their lucky number, it's traditionally lucky in Italy, and in numerology it reduces to 4, a number of solid, dependable work.