Cuboids, Rectangular Prisms And Cubes - Math Is Fun

Cuboids, Rectangular Prisms and Cubes

Go to Surface Area or Volume.

A cuboid is a box-shaped object.

It has six flat faces and all angles are right angles.

And all of its faces are rectangles.

It is also a prism because it has the same cross-section along a length. In fact it is a rectangular prism.

Examples of Cuboids

Cuboids are very common in our world, from boxes to buildings we see them everywhere. We can even fit them inside other cuboids!

A building A box with a slot as a handle Cuboids in a cuboid room Boxes for model trains Now that's just silly!

Square Prism

When at least two of the lengths are equal it can also be called a square prism.

(Note: we can still call it a rectangular prism if we want!)

Cube

When all lengths are equal (and all angles are right angles) it is a cube (or hexahedron) and each face is a square.

A cube is still a prism.

And a cube is one of the Platonic Solids.

So:

• A cube is just a special case of a square prism, and
• A square prism is just a special case of a rectangular prism, and
• They are all cuboids!

The name "cuboid" comes from "cube" and -oid (which means similar to, or resembling) and so says "it is like a cube".

Another use of -oid is when we talk about the Earth being a spheroid (not exactly a sphere, but close).

Surface Area

The surface area is found using the formula:

Area = 2 × Width × Length + 2 × Length × Height + 2 × Width × Height

Which can be shortened to:

A = 2wl + 2lh + 2hw

Example: Find the surface area of this cuboid

A = 2wl + 2lh + 2hw = 2×4×10 + 2×10×5 + 2×5×4 = 80 + 100 + 40 = 220

Volume

The volume of a cuboid is found using the formula:

Volume = Length × Width × Height

Which can be shortened to:

V = l × w × h

Or more simply:

V = lwh

Example: Find the volume of this cuboid

V = lwh = 10 × 4 × 5 = 200

Example: Sam wants to refill the fish tank

It is 140 cm wide and 50 cm front-to-back. The water depth is 60 cm:

V = lwh = 140 cm × 50 cm × 60 cm = 420,000 cm3

A liter is 1,000 cm3, so that is 420 liters of water

859,860,1816, 1817, 1818, 1819, 1820, 1821, 1822, 1823 Cube (Hexahedron) Prisms Geometry Index