Outer faces and curved surfaces
Cone Surface Area Calculator
Enter the radius or diameter and either vertical height or slant height. Include the circular base or calculate only the curved surface.
Enter your measurements
Explore surface area calculators
Cone surface area formula
The curved or lateral area is πrs, where r is radius and s is slant height. Adding the circular base gives A = πrs + πr².
For a right circular cone, slant height is s = √(r² + h²), with h measured perpendicular to the base. If you know slant height already, select that option. It must be greater than the radius for a cone with positive vertical height.
Example: radius 3 ft, vertical height 4 ft
Slant height = √(3² + 4²) = 5 ft. The curved surface is 15π ≈ 47.12 ft². Including the base gives 24π ≈ 75.40 ft².
Vertical height and slant height are different
Vertical height runs from the base center to the tip. Slant height follows the side from the tip to the base rim. The formula for surface area uses slant height, while the cone volume formula uses vertical height.
Choose “Curved side only” for an open cone without a base. This tool assumes a right circular cone and does not calculate a truncated cone or an oblique cone.
To find the space inside, use the cone volume calculator.
Enter every length in the same unit. Results are rounded for display; calculations use unrounded values and the full precision of π.