For those math enthusiasts, Pi was originally defined as the ratio of a circle's circumference to its diameter, but it now has various definitions and appears in many formulas in mathematics and physics.
Fresh Brothers: Grab a personal pizza with unlimited toppings for $3.14 at Fresh Brothers in Carmel Valley, using the promo code "PIDAY".
Mountain Mike's is offering $5 off any "mountain-sized" pizza (that's a really big pizza) and $3 off any large-sized pizza.
Mellow Mushroom: Get a small cheese pizza for $3.14 with any other pizza purchase.
Biggby Coffee: The Apple Pie latte is returning and will be $3.14.
We've compiled a list of the best places to score a deal on a pie this Pi Day, so take a peek and see if there are any being served up near you. Guests can present a coupon - which is available to download on the Marie Callender's website - to choose from 20 different varieties of pie.
The spot says all pizzas will be $3.14 on Thursday. You can also buy an entire pizza pie and earn 314 points for the app, according to USA Today.
Today marks the celebration of Pi, or π, that mathematical number 3.1415....you get the idea.
Pieology Pizza: Buy one artisan thin crust pizza, get another for $3.14.
The meal kit service is offering a pretty sweet Pi Day deal for first time subscribers: free dessert for a year!
For those who don't like pie very much, it also happens to be National Potato Chip Day.
If you download Blaze Pizza's new app, you can order a pizza for $3.14-the deal is good for one pie person, and gluten-free pizzas are included in the Pi Day deal too. Just bring a coupon with you and enjoy.