Now Pi Day March 14 (3.14) has become International Day of Mathematics as well. Let’s celebrate with math books and activities!

Pi is based on the relationship (ratio) between circumference of a circle and its diameter. If you’re a bit rusty in math, the diameter is a straight line segment that passes through the center of a circle and has endpoints on the circle. The circumference is the distance around the outside of the circle.

π = C/d

It is a fascinating number because it is so useful, but it is also irrational. That means it is an infinite, non-repeating decimal.

Pi Day activities can run the gamut from serious to seriously lighthearted.

You might want to check out

One great way to celebrate Pi Day is to read a book about math. See our growing list of children’s math books for Pi Day and every day at Science Books for Kids and our list of Women Who Count, biographies of women mathematicians (also useful for Women’s History Month).


Visit our Pi Day Pinterest Board for even more ideas.