What is Pi? Understanding This Important Part of Maths


  1. What is the value of pi?
  2. How do you use the pi value in maths?
  3. How was pi discovered?
  4. What is pi used for in everyday life?
  5. Pi is an important part of maths

What is pi? No, we’re not misspelling your favourite winter dinner. 🥧 We’re talking about maths

You’ve probably heard this term in your geometry classes before, but how much do you really know about pi? 

In short, pi is a mathematical constant, which means its value never changes. If you’re wondering about the value of pi, how pi was discovered, or the uses of pi in real life, we’re here to break it all down for you.maths-lernen-1-1

What is the value of pi?


Pi is written as the Greek symbol π. If you’re wondering what does pi mean in Greek, it’s the letter “p!”

Pi is the ratio of the circumference of any circle to the diameter of that circle. Regardless of the circle’s size, this ratio will always equal pi. Basically, if you’re determining the size of any part of a circle, pi is essential. (If you’re confused, don’t worry–we explain more below!) 

What’s the numerical value of pi? In decimal form, the value of pi is approximately 3.14. It’s an irrational number though, which means it doesn’t end (like ½ + 0.50) or become repetitive (like ⅓ = 0.3333…). 

The full value of pi goes on forever. Yes, forever! Because pi is an irrational number, it has an infinite number of decimal places, and the numbers are all seemingly random. 

For example, pi to 18 decimal places is 3.141592653589793238! However, 3.14 is the standard numerical representation of mathematical pi–and is much easier to remember, too! 


How do you use the pi value in maths?


Once you know what mathematical pi is equal to, you can better use it in maths! Pi is related to circles, and here are some common ways you’ll use it:

Divide the circumference of a circle by the diameter to get pi

No matter what size your circle is, circumference (the distance around a circle) divided by diameter (the distance across a circle) will always equal pi! Take the following example, where the diameter of the circle is 10 cm, and the circumference is 31.41 cm.


C ➗ d = pi

31.41 ➗ 10 = 3.141. 

3.141 = π

So, by dividing the circumference (31.41) by the diameter (10), we found pi!

Use pi to find the circumference when you know the diameter 

Know the diameter but not the circumference? Pi will help with that! 

Circumference (C) is equal to π x diameter (d), or C = π x d. There’s a clever way to remember this formula, too: Cherry (C) pie’s (π)  delicious (d)! 

Here’s an example, where the diameter of the circle is 20 m:


C = π x d

C = π x 20 

C = 62.83 m 

So, by multiplying pi by the diameter (20 cm), we found the circumference of the circle, rounded to 2 decimal places (62.83 m)

If you know the circumference but not the diameter, you can do the same equation, just in reverse, by dividing the circumference by pi. Using the same example:

d= C ➗ π

d= 62.83 ➗ π

d= 19.99, rounded up to 20 m!

Find the area of a circle with pi

Pi can also be used to find the area of a circle. The area of a circle is pi times the radius squared or A = π x r2. The radius is one-half of the diameter of a circle. 

There’s another clever way to remember this formula! We already learned cherry pie’s delicious (C = π x d), but now, we learn that apple pies are, too (A = π x r2 )! 

Here’s the equation in action:


A = π x r2

A = π x 52

A = π x 25

A = 78.54 m

So, we used pi and the radius to find the area!

As you’ve seen, pi is very useful in maths. But for how long has pi been around?


How was pi discovered?


Pi is much older than you may think! Who discovered pi first? Ancient Greek mathematician Archimedes of Syracuse is credited with doing the first calculation of pi–all the way back in the third century B.C.!

It took centuries for more research to be done on pi. In 1665, Sir Isaac Newton recorded 16 digits of pi, the biggest development since Ancient Greece. It wasn’t until the 18th century that the word “pi” came to be and its symbol π. It was created by British mathematician William Jones in 1706, and popularized by Swiss mathematician Leonhard Euler a few decades later. 

Today, pi is taught to students in maths classes worldwide. It’s an important part of geometry, but many students may not see how it's relevant in real life. However, there are many uses of pi in real life!


What is pi used for in everyday life?


Pi has many real-life uses. Without it, there are many things we wouldn’t understand about our world, and things that wouldn’t exist! Uses of pi in real life include: 

  • Astronomy. Pi is how scientists were able to discover the rotation of Earth and its orbits! It’s also how astronomers study other existing planets and even find new ones.
  • Sound & Light. Pi is found in the sine waves that process the signals in sound and light waves, including the ones that allow us to watch television!
  • Construction. If a building or structure contains curves, pi is used to help ensure the building and all its parts are safe and efficient.
  • Manufacturing. Whether you’re making a swimming pool, a basketball, or a car tire, pi is used to build and create these circular objects!


Pi is an important part of maths


Pi may seem a bit confusing with its infinite decimal places, but it’s not as complicated as it may seem!

All you need to remember is π = 3.14, and those two special formulas:

  • C = π x d (Cherry pie’s delicious!)
  • A = π x r2 (Apple pies are, too!)

Once you get the basics down, pi can actually be a lot of fun! If you need a little help mastering pi, though, GoStudent is your solution. We have the best math tutoring online, and we’ll help you become an expert in no time! Sign up for our free trial lesson today and see how we can help you become a premier pro at pi. 🥧