The number π (/ paɪ / ⓘ; spelled out as pi) is a mathematical constant, approximately equal to 3.14159, that is the ratio of a circle 's circumference to its diameter.

The first million digits of pi (π) are below. Why not calculate the circumference of a circle using pi here. Or simply learn about pi here. Maximize the fun you…

Mar 2, 2026 · pi (π), in mathematics, the ratio of the circumference of a circle to its diameter. The Greek letter π was first used by British mathematician William Jones in 1706 to represent the ratio …

Then the circumference (all the way around the circle) is 3.14159265... a number known as Pi. Pi (pronounced like "pie") is often written using the Greek symbol π. With a diameter of D the …

2 days ago · Celebrate Pi Day and read about how this number pops up across math and science on our special Pi Day page. For more than two millennia, mathematicians have produced a growing …

5 days ago · For Pi Day, Mathematics Professor Adrian Rice answered our questions about the history and uses for the number pi.

2 days ago · The Pi Day was created in 1988 by Larry Shaw, a physicist at the Exploratorium science museum in San Francisco.

Pi is a constant value. That is, the ratio of the circumference to the diameter is the same for all circles. The drawing below shows the circumference of a circle that has been "straightened out." It is a little …

The Greek small letter π (pi) is used in trigonometry as a constant to represent a half-rotation around a circle in radians. The value of π is approximately 3.14159 and appears in many math formulas and …

The 1998 film Pi is a dark, strange, and hyperkinetic movie about a mathematician who is slowly going insane searching for a pattern to the Stock Market. Both a Hasidic cabalistic sect and a Wall Street …