New York CNN  —  Pi Day isn’t just about showing off how many numbers you have memorized – restaurants from Burger King to California Pizza Kitchen are offering deals and discounts on Thursday, March 14th. Pi Day occurs on March 14, because the date is written as 3.14 in the United States. Pi is the ratio of the circumference of a circle to its diameter, or approximately 3.14 (its exact value is infinite and can’t be calculated). March 14 also happens to be Albert Einstein’s birthday. With eating out become more of a luxury, restaurants use such deals to help draw customers to fast casual and fast food chains. Pi Day has also become synonymous with pizza pie (and other round foods) – here are some deals to round out your celebration. Pizza Hut From March 12-14, Pizza Hut has been offering a free large one-topping pizza with purchase of a large menu-priced pizza. 7-Eleven Loyalty members can get any flavor large pizza for $3.14 in 7-Eleven, Speedway and Stripes stores – limited to one transaction, two per day. BJ’s Restaurant & Brewhouse Dine-in customers at BJ’s Restaurant & Brewhouse can get a mini one-topping pizza for $3.14. Blaze Pizza Build-your-own-pizza chain Blaze is offering an 11-inch pizza for $3.14 in-store at participating locations. Burger King As part of its week of breakfast deals, Burger King is offering a free Hershey’s sundae pie with a $3.14 purchase. California Pizza Kitchen CPK rewards members can get an Original BBQ chicken, pepperoni, or traditional cheese pizza for $3.14 with a dine-in purchase of $25.