The surface area of a cone can be calculated using the formula $$S=\pi r^2+\pi r\ell ,$$ where $r$ is the radius of the base area of the cone and $\ell$ its slant height.

The cone's surface area can be seen as two separate parts: the base and the lateral surface. The area of the base is given by $\pi r^2$ and the lateral surface has the area $\pi r\ell .$