Lesson 4: Volume of Cylinders and Cones

Property

Volume is the amount of space contained within a three-dimensional object. It is measured in cubic units, such as cubic feet or cubic centimeters.

Cylinder Volume Formula:

Property

A cone is a three-dimensional shape with a circular base and an apex. The volume of a right circular cone is one-third the product of the area of the base and the height. If the height is $h$ and the radius of the base is $r$, then $V = \frac{1}{3} \pi r^2 h$.

Examples

• A party hat is a cone with a height of 8 inches and a base radius of 3 inches. Its volume is $V = \frac{1}{3} \pi (3^2)(8) = 24\pi$ cubic inches.
• A cylinder has a volume of $90$ cubic cm. A cone with the same base and height would have a volume of $V = \frac{1}{3} (90) = 30$ cubic cm.
• An hourglass cone holds $15\pi$ cubic inches of sand and has a base radius of 3 inches. Its height is found by solving $15\pi = \frac{1}{3} \pi (3^2)h$, which gives $h=5$ inches.

Explanation

A cone's volume is directly related to a cylinder's. For a cone and cylinder with the same base radius and height, the cone's volume is exactly one-third of the cylinder's. You could fit three full cones of water into one cylinder.

Property

A cone has exactly one-third the volume of a cylinder with the same base and height: $V_{cone} = \frac{1}{3} \cdot V_{cylinder}$

If cylinder volume is $V_{cylinder} = \pi r^2 h$, then cone volume is $V_{cone} = \frac{1}{3}\pi r^2 h$