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…

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.

Dec 10, 2025 · 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 …

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 …

Draw a circle with a diameter (all the way across the circle) of 1. Then the circumference (all the way around the circle) is 3.14159265... a number known as Pi. Pi (pronounced like "pie") is often written …

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 …

It is defined as the ratio of a circle's circumference to its diameter, and it also has various equivalent definitions. It appears in many formulas in all areas of mathematics and physics. It is approximately …