Pi Day: US honours mathematics with pizza and pie

7-Eleven and Whole Foods offer 3.14-themed deals to mark day lining up with mathematical constant

As pi is a homophone for 'pie', the celebration has naturally expanded to include all circle-shaped foods. AP

March 14 — or 3/14 according to the US calendar — is Pi Day, a national celebration of mathematics.

Pi (π) is a mathematical constant, the ratio of the circumference of a circle to its diameter, and is commonly represented by the number 3.14, though, as an irrational number, its digits never end.

The earliest reference to the constant using the Greek letter pi was first used by mathematicians in the 18th century, though its usage goes back thousands of years.

In August 2021, mathematicians using a supercomputer in Switzerland found that the consonant number had at least 62.8 trillion digits. The previous record was 50 trillion figures.

But it's not all about maths. As pi is a homophone for “pie”, the celebration has naturally expanded to include all circle-shaped foods.

In popular culture, people mark the day by eating pie or pizza — even though National Pie Day is on January 23 and National Pizza Day is on February 9.

Restaurants and chains in the US often give discounts on pies or pizzas to mark the mathematical occasion.

Whole Foods is giving $3.14 dollars off for any Amazon Prime member who purchases a pie at a location on Monday.

McDonald's is also giving away free pies for anyone making a purchase over $1.

National convenience store chain 7-Eleven is selling whole pizzas for $3.14 if the customer is a 7Rewards loyalty programme member.

“Our $3.14 Pi Day pizza promotion has become a tradition that our customers look forward to year after year,” 7-Eleven fresh foods director Deanna Hall said in a statement

“Not only is Pi Day a fun and quirky maths holiday, but it’s a great opportunity to showcase our great quality pizza.”

The day is also special for scientists: it's Albert Einstein's birthday and Stephen Hawking died on this day.