The Golden Mean: Fun with Grandkids

The Golden Mean: Fun with Grandkids

Have you ever heard of the Golden Mean?

Uppercase and lowercase Greek letter phi

Photo Credit: Wikipedia

It is sometimes called the Golden Ratio. It is a line divided at the point where the ratio of the smaller part to the larger part is the same as the larger part to the whole. Like pi, it is constant, so it is always about 1.618. And, like pi, its value to the right of the decimal point continues, without the digits repeating a pattern. It is called phi, also written as a Greek letter.

How Can You See It?


  • Belly buttons
  • Yardstick or measuring tape
  • Pencil or pen
  • Paper
  • Calculator or the ability to do long division


  • Measure the distance from the floor to your grandchild’s belly button
  • Measure the distance from the floor to your belly button
  • Measure your grandchild’s height
  • Measure your height
  • Divide your grandchild’s height by the distance to their belly button
  • Divide your height by the height to your belly button

What Should Happen?

The ratio between the height of your belly button from the floor and your height should be about 1.618.

For us, it was close.

  • Height to my grandson’s belly button: 30.5 inches
  • My grandson’s height: 49.5 inches
  • Divide second, or larger, number by first: 1.6229
  • Height to Grandma’s belly button: 39 inches
  • Grandma’s height: 64.5 inches
  • Divide second, or larger, number by first: 1.6538

How Is Phi Used?

Phi is used in mathematics, architecture and sculpture. It is said to have been used in the construction of the Great Pyramid of Giza, in Egypt. The ratio of the height of the pyramid to the size of the base is phi. The Parthenon in Greece, the Notre Dame Cathedral in Paris, the Taj Majal in India and the United Nations building in New York City all used phi in their designs, for its pleasing proportions.

Carol Covin, Granny-Guru, Author, “Who Gets to Name Grandma?”


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Comments (5 )

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  1. findingourwaynow says:

    I do love how you take something complex and turn it into a fun lesson that can be easily understood and remembered. Bravo. 🙂

    • carolcovin says:

      Thank you so much! I'm not a teacher, but I tried to get my kids ready to understand what the teacher taught them and now I like to do the same for my grandchildren.

  2. JeriWB says:

    I guess I just learned something new today 😉

  3. I am so not a math person. I have never heard of phi before.

  4. carolcovin says:

    Jon, If you're a photographer, you may have heard of the rule of thirds, where you divide a photo you're framing into a 3×3 grid and put the thing you want to highlight at one of the intersections. Phi is about 2/3 and is all about what looks good.