# Surface Area of Cone

To calculate the **surface area of a cone** we need to know its radius or diameter, the pi number (3.1415...) and length of its side. The **surface area of a cone** is a phrase which express a largeness of a surface around a cone solid. For example, we can use a formula of the **surface area of a cone** to count how many metres of paper we need to make a witch hat. The elementary unit of the surface area is one square metre, it means the second power of one metre (1 m^{2}).

## Surface Area of Cone - formula

**Surface Area of Cone** = 1/4 × Ludolph's number × diameter × (diameter + 2 × side length)

or

**Surface Area of Cone** = Ludolph's number × radius × (radius + side length)

S = 1/4 × π × d × (d + 2 × s) = π × r × (r + s)