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Last updated on August 30, 2025

Surface Area of Polyhedron

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A polyhedron is a 3-dimensional shape with flat polygonal faces, straight edges, and vertices. The surface area of a polyhedron is the total area covered by its outer surface. In this article, we will learn about the surface area of polyhedra, including how to calculate it for various types of polyhedra.

Surface Area of Polyhedron for US Students
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What is the Surface Area of a Polyhedron?

The surface area of a polyhedron is the total area occupied by the boundary or surface of the polyhedron. It is measured in square units.

A polyhedron is a 3D shape with flat surfaces called faces, straight edges, and vertices.

Polyhedra can be classified into different types, including regular polyhedra (Platonic solids) and irregular polyhedra.

The surface area of a polyhedron is calculated by summing the areas of all its faces.

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Surface Area of a Polyhedron Formula

To calculate the surface area of a polyhedron, add up the areas of all its individual faces.

Each face is a polygon, and the area can be calculated based on the type of polygon (e.g., triangles, squares, rectangles).

The formula for the surface area of a polyhedron depends on the number and shape of its faces.

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Surface Area of Regular Polyhedra

Regular polyhedra, also known as Platonic solids, have faces that are congruent regular polygons.

Examples include the tetrahedron, cube, and dodecahedron.

The surface area of a regular polyhedron can be calculated using the formula:

Surface Area = n × A

Here, n is the number of faces, and A is the area of one face.

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Surface Area of Irregular Polyhedra

For irregular polyhedra, the surface area is calculated by finding the area of each face and summing them up.

Since the faces may not be congruent or regular, each face might require a different method to calculate its area, depending on its shape.

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Volume of a Polyhedron

The volume of a polyhedron shows how much space is inside it. It depends on the shape and size of the polyhedron.

For regular polyhedra, specific formulas based on the type of solid can be used to calculate volume.

For irregular polyhedra, methods like decomposition into simpler shapes or using calculus might be necessary.

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Confusion between Faces and Edges

Students sometimes confuse the number of faces with the number of edges. Remember that the surface area involves calculating the area of each face, not the length of edges.

Mistake 1

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Using Incorrect Formulas for Irregular Polyhedra

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For irregular polyhedra, students might use formulas meant for regular polyhedra, leading to errors. Ensure the method used matches the specific type of polyhedron.

Mistake 2

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Forgetting to Sum All Face Areas

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Students often calculate the area of only some faces and forget others, especially in complex shapes. Always verify that the area of every face is included in the total.

Mistake 3

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Incorrect Polygon Area Calculations

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When calculating the area of each face, students might use incorrect formulas for polygons, such as triangles or trapezoids. Be sure to apply the correct area formula for each type of face.

Mistake 4

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Assuming All Polyhedra Are Regular

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Some students assume all polyhedra are regular, using simpler formulas. Recognize when a polyhedron is irregular and requires more complex calculations.

Mistake 5

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Solved Examples of Surface Area of Polyhedra

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Find the surface area of a cube with each side measuring 4 cm.

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SA = 96 cm²

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Problem 1

A cube has 6 congruent square faces. Area of one face = 4 × 4 = 16 cm² Surface Area = 6 × 16 = 96 cm²

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Calculate the surface area of a regular tetrahedron with each edge measuring 3 cm.

Explanation

SA = 15.59 cm²

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Problem 2

A regular tetrahedron has 4 equilateral triangle faces. Area of one face = (√3/4) × 3² = 3.897 cm² Surface Area = 4 × 3.897 = 15.59 cm²

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A rectangular prism has dimensions 5 cm, 3 cm, and 2 cm. Find the surface area.

Explanation

SA = 62 cm²

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Problem 3

Surface Area = 2(lw + lh + wh) = 2(5×3 + 5×2 + 3×2) = 2(15 + 10 + 6) = 2 × 31 = 62 cm²

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Find the surface area of a cylinder with a height of 8 cm and a base radius of 3 cm.

Explanation

SA = 207.72 cm²

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Problem 4

Surface Area = 2πr(h + r) = 2 × 3.14 × 3 × (8 + 3) = 6.28 × 3 × 11 = 207.72 cm²

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Determine the surface area of a regular octahedron with an edge length of 2 cm.

Explanation

SA = 13.86 cm²

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It is the total area covering the outer surface of the polyhedron, calculated by summing the areas of all faces.

1.What is the difference between regular and irregular polyhedra?

Regular polyhedra have congruent regular polygonal faces, while irregular polyhedra have faces of different shapes or sizes.

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2.How do you calculate the surface area of a polyhedron?

By adding the areas of each of its polygonal faces, using the appropriate area formula for each polygon type.

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3.What are Platonic solids?

Platonic solids are a special class of regular polyhedra with congruent faces of regular polygons and the same number of faces meeting at each vertex.

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4.What unit is surface area measured in?

Surface area is always measured in square units like cm², m², or in².

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Common Mistakes and How to Avoid Them in the Surface Area of Polyhedra

Students often make mistakes while calculating the surface area of polyhedra, which leads to incorrect answers. Below are some common mistakes and the ways to avoid them.

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Seyed Ali Fathima S

About the Author

Seyed Ali Fathima S a math expert with nearly 5 years of experience as a math teacher. From an engineer to a math teacher, shows her passion for math and teaching. She is a calculator queen, who loves tables and she turns tables to puzzles and songs.

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: She has songs for each table which helps her to remember the tables

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