Pi Day Activities: Real-World Uses of Pi in STEM

When a mathematical ratio has its own holiday, you know there’s something special about it! On Pi Day (March 14), we celebrate the ubiquity and usefulness of pi (π) throughout the world.

What Is Pi?

How does pi (3.1415926….) help us in everyday life? Pi Day 2025 on March 14 is the perfect time to solve the equation!

Pi (π) is a ratio used by scientists, engineers, mathematicians, and computer scientists to help calculate the circumference, area, and volume of circles, spheres, and curves. From mapping planetary bodies and designing prosthetic limbs to positioning satellites, we use this ratio to answer questions about our universe and create solutions that improve the world around us.

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Professional Pathways that Utilize Pi

Whether used directly or indirectly through other formulas, professionals in many STEM careers rely on the ratio to create safe, functional products and design innovative solutions.

• Materials engineers use pi to design parachutes that generate the proper amount of drag necessary to safely land in specific environments 
• Architects use pi to determine the amount of material needed to build a circular structure such as a light pole or grain silo
• Planetary scientists and astrophysicists use pi to calculate the distance between two orbiting objects, such as a planet and star
• Satellite systems engineers use pi to help determine the proper positioning of satellites to ensure connectivity and communication
• Prosthetists and orthotists use pi to calculate volume and surface area, which helps them design prosthetics, implants, and medical devices
  

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Your PLTW Pi Day Plan

Here are some fun ways to engage your students with Pi Day. Click here to download the PLTW Pi Day Planner as a PDF.

Get a Piece of the Pi! | Elementary (PreK-5) Activity

Show students how to measure pi using everyday objects!

Supplies: One (1) round object such as a lid or cup, one (1) piece of string longer than the circumference of the object, one (1) pair of scissors, tape (optional)

• Measure the Circumference: Wrap a piece of string around your object one time, until it reaches the starting point. Cut the string where it meets the start. If needed, use tape or teamwork to hold one end down while cutting the string.
• Measure the Diameter: Stretch the string across the center of the object at its widest point to measure the diameter (or width) of the circle. Cut the string to the diameter of the object. Do this step two more times.
• Find the Pieces of Pi: Notice the very small, .14 length of string that was left after measuring the diameter three times. This represents the circumference of your circle, which is 3.14 times longer than the diameter of a circle.
• Discuss Your Results: Compare your experience with classmates. Discuss whether or not this experiment would work with other circular objects.

Learn more about Pi Day from PBSKids

The Proof is in the Pudding Pi | Middle School (6-8) Activity

Tap into middle school students’ curiosity by asking them to prove that pi is a constant.

To get middle school students engaged in Pi Day, complete the same steps as listed above in the “Get a Piece of the Pi!” activity using multiple objects of varying sizes.

See this activity in action (with a real pie!)

What’s Your Favorite Flavor of Pi? | High School (9-12) Activity

High school students want to know why they need to learn certain concepts such as pi, and that context is critical for students as they explore interests and future careers. Prompt your students to research how real people use pi to solve problems and design solutions—from medical innovation and building design to space exploration.

Find more real-world learning in this library of free STEM activities

Pi Day is a great time to circle up and share the “why” behind pi. By giving this technically irrational number real-life context, you’ll spark curiosity as students unlock a deeper understanding of the world. Happy celebrating!