Making pies for Pi Day: Think inside the circle

Updated March 14, 2023 at 4:13 PM ET

Editor's note: A version of this story was published in March 2011.

Get ready to roll out some dough, because it's Pi Day.

What's that, you ask? Think back to geometry class. Pi represents the ratio of a circle's circumference (the distance around the circle) to its diameter (the distance across it). In mathematics, it's been represented by the Greek letter "π" since the 1700s.

For the math challenged, think of something that's round. Might I suggest ... pie? It's the perfect example because, in addition to being round, it's pronounced the same way as pi. And you can even use pies to calculate Pi, more or less, as this video shows:

Now, it's been a long time since I sat in math class and learned about pi. Here's what I remember: The value of pi is about 3.14159. (The value of pie, on the other hand, is, of course, deliciousness.) Pi is often shortened further to 3.14, but it actually goes on forever.

Some genius grasped the idea before I did and started Pi Day — which, of course, is celebrated with pie.

But when to celebrate it? Well, the number 3.14, in terms of the calendar, translates to the third month and the 14th day — which means March 14. It's been further suggested that 1:59 is the perfect time to celebrate, reflecting a few more places after the decimal.

Pi plates, T-shirts and other retail items are helping Pi Day supporters take their math-themed celebration mainstream.

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While I'm still a little bummed that I didn't come up with Pi Day, I have jumped on this holiday bandwagon. There are mathematics competitions, pi jewelry-making lessons and — no surprise here — pie-eating contests. I even participated one year in a Pi Fun Run. (And by "participate," I mean I walked; apparently pie isn't the breakfast of champions.)

Businesses that promote math, science and technology offer promotional Pi Day discounts. You can buy pi pie plates and clever pi T-shirts.

With all of those marketers on board, it's just a matter of time before we all — not just math enthusiasts — celebrate the day. I choose to believe that Pi Day is just overshadowed by St. Patrick's Day. I mean, come on — if you can count clover leaves, you can slice up a pie without any problem. Yes, pie — if not pi — really is easy.

Don't believe me? Try it out for yourself with some of my favorite recipes below — including one that elevates mincemeat pie to the 10th power.

Doreen McCallister is a senior editor for NPR. For dozens of years, she's been keeping her NPR colleagues guessing about her baking experiments. Prod her on the secret ingredient in her extra-moist, scrumptious baked goods, and you're liable to get an answer like mayonnaise, tomato soup or even Velveeta. Even when she brings something "normal" to work, everyone demands to know: "What's in it? No, really — what's in it?" Whatever the secret, it's always delicious.

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