About this tool
Calculate the surface area of common 3D solids. Choose a shape, enter its dimensions, and the tool returns the total surface area, the lateral (side) surface area where it applies, and the slant height for cones and pyramids. It works for a cube, rectangular box, sphere, cylinder, cone, square pyramid and triangular prism, all in your browser.
The formulas are exact: cube 6s²; box 2(lw + lh + wh); sphere 4πr²; cylinder 2πr² + 2πrh total with 2πrh lateral; cone πr² + πr·l where the slant l = √(r² + h²); square pyramid b² + 2b·√((b/2)² + h²). The triangular prism uses two triangular ends found with Heron's formula plus the three rectangular sides, giving 2·area + (a + b + c)·L, with lateral area (a + b + c)·L.
All dimensions must be positive, and a triangular prism needs three sides that actually form a triangle. Surface area comes out in square units of whatever length unit you enter.