To some people, Pi Day is about mathematics. To others, it’s an excuse to eat pizza. Either way, there will be celebrations on Friday, March 14. Pi is the ratio of a circle’s circumference to its diameter, named after a Greek letter. It’s a constant number with an infinite number of digits, as explained by the U.S. Census Bureau.

National Pi Day on March 14 throws a spotlight on the pizza sector, which has increasingly used the math-inspired event for promotions to drive extra sales and traffic. Pi Day is celebrated annually on March 14th because the date corresponds to the first three digits of the mathematical constant pi,

While math enthusiasts recognize the date for its significance in geometry, restaurants across the U.S. have embraced National Pi Day by offering special deals on pizza and pie.

March 14 (3/14) is the day we celebrate the mathematical constant pi — 3.14. In honor of the holiday, restaurants across the country offer deals and freebies on pizza and pie. Here are some of the best Pi Day deals on pizza and pie.