Surface area

Math

Definition

The total area of all the faces or surfaces of a three-dimensional figure. Surface area is measured in square units and tells you how much material would be needed to cover the outside of a solid.

Examples

  • A rectangular box 3×4×5 has surface area 2(3·4 + 3·5 + 4·5) = 94 square units
  • A cylinder with radius 3 and height 7 has surface area 2π(3)² + 2π(3)(7) = 60π
  • Calculating how much wrapping paper is needed for a gift box
Key Fact

Rectangular prism: SA = 2(lw + lh + wh); Cylinder: SA = 2πr² + 2πrh

Related Terms

Area of polygons Volume of prisms and cylinders Volume of pyramids and cones

Study This Concept

Practice surface area with free review games in these units:

Geometry Unit 10: Area and Volume