What is Pi?

Pi, or π, is a mathematical constant and represents the ratio between the distance around a circle (this is known as the circumference) and the diameter of the circle, resulting in the same number every time. The number, though, is odd. It starts at 3.14159265... and continues forever. Numbers like this are known as irrational numbers.

When you divide the circumference of any circle by its diameter, the answer (whether for a pizza or football) is always approximately 3.14, which is represented by the Greek letter π.

Where did the symbol come from?

Symbolizing this ratio, the Greek letter π, was devised by British mathematician William Jones in 1706 and popularized by Swiss mathematician Leonhard Euler in the early 18th century.

A Brief History of Pi

In ancient Babylon, the area of a circle was calculated by taking 3 times the square of its radius, which gave a value of pi = 3

According to the Rhind papyrus, ancient Egyptians used the value of 256/81 or about 3.16045

Years later, Archimedes devised a method that could calculate pi to any degree of accuracy. He obtained an average value of about 3.1418 by enclosing and circumscribing regular polygons around a circle.

Archimedes also proved that the ratio of the area of a circle to the square of its radius is the same constant.

As the more time passed, Chinese, Indian, and Arab mathematicians added decimal places by tedious calculations, rather than improving Archimedes' method.

Later on, using the binomial theorem, Sir Isaac Newton figured out Pi to 16 decimal places.

Srinivasa Ramanujan, an Indian mathematician early in the 20th century, developed an extremely efficient way to calculate pi which later became integral to computer algorithms.

Early in the 21st century, computers were able to calculate pi to more than 13,300,000,000,000 decimal places.

How to Calculate Pi

Calculating Pi is quite a simple process. All you need to do is take the measurement of any circle's circumference, and divide it by its diameter.

Pi = circumference divided by diameter

For example: You have measured a circle with the diameter of 12cm, and a circumference of 37.7cm

37.7 ÷ 12 = 3.14

How cool is that?!

How to Find the Area of a Circle using Pi

You can use a simple calculation to find the area of a circle using pi. It looks like this:

How to Find the Circumference of a Circle using Pi

You can also use the following calculation to find the circumference of any circle:

How many Digits are in Pi?

The digits in pi are infinite, which means that it never ends. We currently know more than 13,300,000,000,000 digits of pi.

What are the First 1000 Digits of Pi?

3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066063155881748815209209628292540917153643678925903600113305305488204665213841469519415116094330572703657595919530921861173819326117931051185480744623799627495673518857527248912279381830119491298336733624406566430860213949463952247371907021798609437027705392171762931767523846748184676694051320005681271452635608277857713427577896091736371787214684409012249534301465495853710507922796892589235420199561121290219608640344181598136297747713099605187072113499999983729780499510597317328160963185950244594553469083026425223082533446850352619311881710100031378387528865875332083814206171776691473035982534904287554687311595628638823537875937519577818577805321712268066130019278766111959092164201989

Some people try and remember as many numbers of Pi as possible. Why don’t you try and memorize some of them?

What is Pi Day?

Pi Day is a day dedicated to celebrating the mathematical constant of Pi (3/14), the date chosen for it represents the first three digits of Pi. Interestingly, it also happens to be Albert Einstein’s birthday!

Pi Day was has been around since 1988, and is a day of celebrating the mathematical constant of pi. People get up to pi antics and activities, and of course, eat pie! Schools across America can take part in Pi Day, by completing pi themed activities.

Ways to Celebrate Pi Day

Bake some pies (and measure the diameter and circumference!)
Take part in a Pi Day scavenger hunt
Make some pi-related crafts
Research the history of pi
Make a piece of pi art work

Pi Resources

Here at Twinkl, we have lots of resources and activities to help you teach all about pi. Here are just a few to spark that pi inspiration:

Our Pi Day Teaching Pack has lots of resources for you to use in your Pi Day celebrations. It includes everything you need, including an online scavenger hunt, a delicious apple ‘pi’ recipe, and a Pi Day bracelet craft just to name a few!

This Equation for Area of a Circle Worksheet and Circumference of a Circle Activity are a great way to get students working out the area and circumference of a circle using Pi to help them.

This cool Pi Day City Skyline Art Activity is a great way to create an interesting piece of art using the digits of Pi. It links really well with other mathematical studies, such as graphs.

Check out our Pi Day Activities Blog to find out more about our top pi resources for children in all elementary grades!

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