You may think that pi is an irrational number... and on any given day, you'd be correct.

But on #NationalPiDay, pi is equal to eight slices of cheesy goodness.

According to piday.org, pi (π) is the ratio of a circle’s circumference to its diameter. Simply put, pi is comparing the distance around the outside of a circle to the distance across a circle from one edge to the other.

The distance around a circle is just over three times longer than the distance across, or 3.1459 to be a bit more exact. In recent years, pi has been calculated to over one trillion digits past its decimal, however, only 39 digits past the decimal are needed to accurately calculate the spherical volume of our entire universe, according to piday.org. CLICK HERE to see one million digits of pi.

Thus, we simply round pi to 3.14, landing National Pi Day or National Rounded Pi Day on March 14 every year. And though National Pizza Day is on February 9 and we celebrate National Pizza month in October, with approximately 3 billion pizzas consumed annually in the U.S., we will take any excuse to grab a slice.

Here are some of our favorite pizza pi(e) deals and fun events to celebrate #NationalPiDay:

**Pizza Pi(e) Deals**

Urban Brick's Pizza: All pizzas are $3.14 for the entire day *(offer in store only)*

The 210 Pizza & Burger Bistro: Buy one pizza get one half off. $3.14 drinks all day.

Ray's Pizzaria: $6.99 Large Pizza

Chicago's Pizza: $5.99 for a large 1-topping pizza or $8.99 for a regular three-topping hand-tossed pizza

Marco's Pizza: $3 off $15 order or more *(deals are based on location)*

Pizza Hut: $7.99 for a large two-topping pizza

Domino's: Two items for $5.99 each or a large three-topping carry out pizza for only $7.99.

Papa John’s: Free large pizza coupon when you spend $15 or more *(promo code SWISH)* or 50 percent off all pizzas *(promo code 50PIZZA)*.

Blaze Pizza - Any pi(e) you choose for just $3.14 all day.

**Other Pi(e) Day deals and events**

Museum of Science: Celebrate Science for Pi Day with Museum of Science

NASA: Celebrate Pi Day with NASA and take the Pi Day Challenge

ThinkGeek: Get a free Pi Day T-shirt when you buy items totaling $31.41. Use the coupon code PIOUS.

Zazzle: Take 14 percent off with coupon code 314159265358.