Greek Small Letter Tau

Symbol Format Data
τ Code Point
All symbols


The Greek small letter τ (tau) is used in math as the circle constant to represent a full rotation around a circle in radians. The value of is approximately and can be calculated by dividing any circle’s circumference by its radius. Typically, the symbol appears in an expression like this:

This expression is a formula for the area of a circle. In plain language, this expression can be read as: the area of the circle is equal to one-half multiplied by the constant (tau) multiplied by the radius of the circle squared.



The capital Greek letter Τ (capital tau).


τ (tau)

The circle constant τ (tau) is a geometric constant approximately equal to 6.283. The numeric value is defined as the length of any circle's circumference divided by the length of its radius.

Radian Angle System

Radians are a unit that measures angle using the radius of a circle. One radian is equal to the amount of rotation required to travel the length of one radius along the circumference of the circle.

Area of Circle

The area of a circle is given by one-half multiplied by τ (tau) multiplied by the radius of the circle squared.

Circumference of Circle

The circumference of a circle is given the constant τ (tau) multiplied by the radius of the circle, where τ = 2π.