The π symbol, used the way we know it today, has been around a little over 300 years.

Quick Scoop

  • The idea of the circle’s ratio (circumference ÷ diameter) is more than 4,000 years old, known to Babylonians and Egyptians long before there was a special symbol.
  • Mathematicians used various words and notations for this ratio through ancient Greek times and the Middle Ages, but not the modern π.
  • In the mid‑1600s, some mathematicians began using Greek letters like π in fractions (for example, perimeter over diameter), but not yet as a standalone constant.
  • The first clear use of π specifically for “the ratio of a circle’s circumference to its diameter” is by the Welsh mathematician William Jones in 1706.
  • Leonhard Euler adopted and popularized π in the 1700s, especially in works from the 1730s and 1740s, and that’s when it really became the standard symbol.

So, how long has π been used?

  • As a named constant with the symbol π (in essentially the modern sense): since 1706, so roughly 320 years as of the mid‑2020s.
  • As a widely accepted, standard symbol in mathematics : about 280–290 years, once Euler’s influential books spread the notation in the 18th century.

You can think of it this way: the number behind π is ancient, but the squiggly Greek letter we write today is “only” a few centuries old.

TL;DR: The ratio we call π has been known for around 4,000 years, but the specific symbol π has been used in (roughly) its modern sense since 1706 and became standard later in the 18th century.

Information gathered from public forums or data available on the internet and portrayed here.