Why is Friday the 13th ‘unlucky’?

With Friday the 13th approaching, you may be wondering about the origin behind this mysterious superstition.

Many superstitions are prevalent in our everyday lives: crossing your fingers, knocking on wood, or avoiding walking under a ladder are all things people often do to ward off misfortune. Friday the 13th is considered particularly unlucky and is thought to bring bad luck – but why is this so?

Here, BBC Bitesize takes a closer look at the history and beliefs behind the superstition and why the number 13 is considered lucky and unlucky - depending on who you ask.

In Christianity, the ‘unlucky’ number 13 can be linked to the Last Supper, where Jesus and his twelve disciples gathered and dined. Judas was the last and thirteenth guest to join the group - before betraying Jesus.

In Norse mythology, a banquet hosting twelve gods in Valhalla was also disrupted when a thirteenth guest, Loki, arrived and caused chaos and tragedy amongst the group. Based on these religious and mythological examples, it is often considered unlucky to have thirteen guests at a dinner party.

It is believed by some that the number 13 is also unlucky for disrupting the ‘harmonious’ number 12, rooted in things such as the 12 months of the year, the 12 signs of the zodiac, and 12 apostles.

A lunisolar calendar, for example, combines the monthly lunar cycles of the moon with the solar year – the 12 months based around the Earth’s orbit of the Sun. Because lunar months are around 29.5 days long, every second or third year usually becomes an embolismic year and adds a thirteenth month - a leap month - and differs from the 12-month years we are familiar with.

The taboo around the number 13 is even present in many architectural and design decisions today. In many multi-storey buildings such as hotels, office buildings or flats, the 13th floor is often named ‘12A’ or is skipped completely. Several airlines also do not have a 13th row on their planes.

On the other hand, it is also believed that 13 can be quite a lucky number. In France before the First World War, the number 13 was used as a good luck symbol on postcards and charms, and in Italy, the expression, “fare tredici” (“make thirteen”) means to hit the jackpot and be extremely lucky.

The number 13 is also sometimes called a baker’s dozen, where a thirteenth extra loaf of bread was known as a ‘vantage loaf’ - a buyer’s advantage for receiving 13 loaves instead of 12.

Beyond a dozen - a proposed 13th zodiac sign, Ophiuchus, or ‘Serpent-bearer’, is associated with doctors, healers and physicians based on an affinity with snakes and protection from poisons.

In pop culture, the number 13 has also become associated with musician Taylor Swift, born on 13 December 1989. Used as a good luck charm, in her earlier career Swift would write the number on her hand before performances. Even in her current work, numerous Easter eggs in her music and release dates link to the number 13.

The fifth day in the week, Friday, too has a history of being associated with bad luck. In Britain, Friday was historically known as “Hangman’s Day” – the day of the week executions were scheduled to take place.

In Christianity, Good Friday was also the day of Jesus’ crucifixion. And at least since the 14th century, Friday has been thought of as an unlucky day for embarking on journeys or beginning new projects.

This is expressed in literary works as early as Geoffrey Chaucer’s The Canterbury Tales, where it is said that “and on a Friday fell all this mischance.”

The exact origins of Friday the 13th being considered unlucky are unknown. However, many historians believe the superstition developed from a combination of cultural, religious and historical beliefs associated with both Friday and the number 13.

Today, Friday the 13th is still fuelled by much superstition: the famous 1980 horror film franchise, Friday the 13th, has become a huge part of modern pop culture and created one of the most iconic horror characters of all time, Jason Voorhees. By becoming associated with the horror genre and Halloween in particular, it’s clear to see why the date has become seen as so eerie!

While, for many, Friday the 13th comes and goes without problem, some still heed caution and observe certain practices throughout the day, such as postponing new projects, refraining from making important life decisions, and avoiding travel.

Extreme caution or fear of Friday the 13th is even officially named paraskevidekatriaphobia. Though for such a fearsome day, Friday the 13th is a regular part of our calendars, occurring at least once every year, and can even happen up to three times per annum!

Originally broadcast on 13 April 1984, the BBC Archive video below follows Bob from Peterborough, who is plagued by accidents on Friday the 13th and decides to stay in bed, hoping to avoid another disaster.

BBC Archive offers a unique collection of thousands of archive films, capturing life and events across the UK since the 1940s.

In 2025 there was only one Friday the 13th, in June, and next year in 2027, there will only be one in August.

So far in 2026, there have already been two Friday the 13ths back-to-back in February and March, with a third coming up this November!

This article was written in October 2026

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