Surface Area of a Cone Calculator SA = πr(r + l). Radius Height Surface area 117.69 Slant height 9.487 Step-by-step with your numbers: 1. Values used: 2. Radius = 3 3. Height = 9 4. Surface area = 117.69 5. Slant height = 9.487 Did we solve your problem today? 👍 Yes 👎 No Thanks for the feedback! Base + lateral surface. FAQ Frustum? Use the frustum calculator. Related calculators Cone Calculator Find a cone's volume, slant height and surface area. Cone Volume Calculator V = π r² h / 3. Slant Height of a Cone Calculator l = √(r² + h²).