It’s not irrational to find pizzas for $3.14 Thursday.

March 14 is Pi Day, an annual celebration of the mathematical constant π (pi), which is the ratio of a circle’s circumference to its diameter. The trillion-digit ratio is rounded to 3.14.

Albert Einstein was born on Pi Day and last year noted astrophysicist Stephen Hawking died on the made-up holiday.

Pi Day, not to be confused with Pie Day held in January, is a day with deals on pizza, pastry and pot pies.

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Aside from calculating your savings, it’s a day to have fun with math too, said Syracuse University mathematics professor Graham Leuschke. He said you can search for your birthday in the digits of π and can create a “pi-ku” similar to a haiku poem., which calls itself the official site for Pi Day, has additional ideas for activities to celebrate the day.

What is Pi Day?: Everything you need to know about celebrating

Math fun: This Google employee set a record calculating Pi to 31.4 trillion digits

Pi Day pizza deals

Here are the deals available at participating locations Thursday unless otherwise noted. To be on the safe side, always check with your closest location before heading out. Also, some will require you to have a restaurant’s app or be signed up for emails.

Rotolo’s Pizzeria: Get one-topping eight-inch pizzas for $3.14 Thursday for dine-in only at participating locations. Gulf Coast stores in Alabama are not included.

More deals: Some local pizzerias, smaller chains and bakeries also will celebrate Pi Day with specials. Check social media accounts to find additional offers.

Read the full article to see other businesses offering pi day specials, here.