How to Calculate Surface Area
What is Surface Area?
Surface area is the total area of all faces or surfaces of a 3D object. It determines how much material is needed to cover an object (wrapping paper, paint, fabric) and is important in engineering, packaging, and biology (cell surface-to-volume ratios).
Step-by-Step Guide
- 1Cube: SA = 6s² (s = side length)
- 2Rectangular prism: SA = 2(lw + lh + wh)
- 3Sphere: SA = 4πr²
- 4Cylinder: SA = 2πr² + 2πrh (top + bottom + lateral)
- 5Cone: SA = πr² + πrl (base + lateral, l = slant height)
Worked Examples
Input
Sphere, radius 5 cm
Result
SA = 314.16 cm²
4π(5²) = 100π
Input
Cylinder, r=3, h=10
Result
SA = 244.35 cm²
2π(9) + 2π(3)(10) = 18π + 60π = 78π
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