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…

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 …

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 …

Pi is an irrational number. An irrational number does not have a repeating pattern and does not end, so it can only be approximated. Calculated to one hundred places after the decimal: π ≈ …

π π is the ratio between a circle's circumference and diameter. That is, circumference diameter = π diametercircumference = π. π π is a fundamental constant in mathematics, especially in geometry, …

Learn about the mathematical definition, historical development, and practical applications of Pi (PI). Explore the decimal characteristics of π, digit distribution patterns, and its wide use in science, …