Friday the 13th is the Western world's most famous unlucky day — buildings skip the 13th floor, some people won't travel or sign deals on it. But why? The dread comes from combining two separate old fears: the number 13, and the day Friday. Here's where it comes from.
Want to know which dates it falls on? See Friday the 13th 2026 dates — there are three this year.
Fear #1: the unlucky number 13
The number 13 has been viewed with suspicion for centuries, largely because 12 is seen as a "complete," harmonious number: 12 months, 12 zodiac signs, 12 hours on a clock, 12 apostles. Thirteen is the awkward one that breaks the set.
- In Norse myth, the trickster god Loki was said to be the 13th guest at a banquet, leading to chaos.
- In Christianity, Judas — who betrayed Jesus — is often counted as the 13th to sit at the Last Supper.
The fear even has a name: triskaidekaphobia (fear of the number 13).
Fear #2: Friday
Friday also carried unlucky associations in Western and Christian tradition — it's traditionally held to be the day of the Crucifixion. Old sayings warned against starting voyages or new ventures on a Friday.
Putting them together
Individually, both superstitions are old. But the specific dread of Friday + the 13th together seems to be relatively modern — it became widespread in the 19th and 20th centuries, popularised by novels (notably Thomas Lawson's 1907 book Friday, the Thirteenth) and later cemented by the famous horror film franchise.
The combined fear has its own tongue-twister name: paraskevidekatriaphobia.
Is Friday the 13th actually unlucky?
Statistically, no. Studies have found no real increase in accidents, misfortune or hospital visits on Friday the 13th compared with other days. The "bad luck" is entirely cultural — though the belief is strong enough that some businesses report quieter trading, and a few people genuinely avoid flying or big decisions that day.
Around the world
It's not universal:
- Spanish-speaking countries and Greece: the unlucky day is Tuesday the 13th, not Friday.
- Italy: Friday the 17th is the dreaded one — 13 is sometimes even considered lucky.
Quick answers
Why is Friday the 13th unlucky? It combines two old superstitions — the unlucky number 13 (the "odd one out" after the complete 12) and Friday (traditionally an unlucky day).
What is the fear of Friday the 13th called? Paraskevidekatriaphobia. The fear of the number 13 alone is triskaidekaphobia.
Is Friday the 13th actually unlucky? No — studies find no real rise in accidents or misfortune. The belief is purely cultural.
Is it unlucky everywhere? No. In Spain and Greece it's Tuesday the 13th; in Italy it's Friday the 17th.