Common Geometry Constants
Useful constants and relationships for circles, triangles, polygons and solids.
| Constant / shape | Value / formula | Use |
|---|---|---|
| π | 3.141592653589793 | Circle circumference/diameter; area formulas |
| τ | 6.283185307179586 | 2π; one full turn in radians |
| √2 | 1.414213562373095 | Diagonal of a unit square |
| √3 | 1.732050807568877 | Equilateral-triangle geometry |
| φ | 1.618033988749895 | Golden ratio |
| Circle | C = 2πr; A = πr² | Circumference and area |
| Triangle | A = bh/2 | Area |
| Pythagorean theorem | a²+b²=c² | Right triangles |
| Sphere | V=4πr³/3; A=4πr² | Volume and surface area |
| Cylinder | V=πr²h | Volume |
How to use this table
Useful constants and relationships for circles, triangles, polygons and solids. Use it as a reference, for practice, or to check your own work. On large tables, scroll horizontally on a phone. Tap cells to visually track a row or value.