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The 14th of March is Pi Day – a special day to celebrate the world’s most famous number. As well as being Pi Day, it is also the International Day of Mathematics, which is celebrated in over 90 countries worldwide.

Here is an easy Pi Day Craft to help you mark this important day – follow these simple steps to create your own square envelope out of circles. Finish off your envelope by adding your own message wishing your friends Happy Pi Day.  You could even write a Pi-ku poem in celebration of Pi Day and put it inside.

You can also download these steps as a Worksheet.

How To Make a Square Envelope Out of Circles

Step 1. Create four circles

Set your compasses to 5cm. (This will give a square envelope with side length 10cm.)

Tip: The side of your envelope will be the same as the diameter of your circle. It is easy to design your own envelope in a different size.

Now draw four identical circles and cut them out. If you have coloured paper, choose two different colours and draw two circles in each colour.

Tip: If you only have plain white paper, it is probably easier to colour in your circles now, before you start folding.

Step 2. Fold the circles

Fold each of your four circles in half.

Fold each of your four circles in half again, so that they are now in quarters.

Step 3. Glue the circles

Arrange the four circles so they overlap – gluing them one at a time into place.  Don’t use too much glue, as you can always add more in afterwards.

Tip: Make sure your central square has right angles, with the fold lines matching up.

Step 4. Write your greeting

Make a note wishing your friends Happy Pi Day and add it to your envelope.

Step 5. Seal up the envelope

Close up your envelope. You do not need to glue it down.


  • First check that you drew four circles which are all the same size.
  • If your envelope still doesn’t sit flat, peel back the last circle you added and trim a tiny bit off the edge. Nobody will notice!



Image: The Pi-ku is based on the traditional Japanese Haiku Poem

You might also like to write a Pi-ku to go inside your envelope. A Pi-ku is similar to a Haiku poem, except it has three lines and follows a 3,1,4 pattern of syllables, in honour of the digits of Pi. To be a true Pi-ku it should be about Pi or circles.

Example Pi-ku (3,1,4 Pattern)

Circles are                          (3 Syllables)

Loved                                  (1 Syllable)

They are like gold            (4 Syllables)

Longer Pi-ku

Some people like to go for the longer 6 line 3,1,4,1,5,9 pattern when writing a Pi-ku.

Example Pi-ku (3,1,4,1,5,9 Pattern)

Round and round


Said the whirlpool


It is part of me

Circles in circles, dancing whirling.

More Pi Day Crafts

If you enjoyed making this envelope out of circles, have a go at making a Pi Day Sphere.


Article by Hazel Lewis

Haiku image – Matsuo Basho, Public domain, via Wikimedia Commons