Volume Formulas | Lesson 1 of 2

Volume of Cylinders and Cones

Lesson 1 of 2: The Base-Times-Height Family

In this lesson:

  • Find the volume of a cylinder
  • See why a cone is one-third of a cylinder
Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

What You Will Be Able to Do

By the end of this lesson, you should be able to:

  1. Use to find a cylinder's volume
  2. Explain why a cone is one-third of a cylinder
  3. Use to find a cone's volume
Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Does Base Times Height Still Work?

A cylindrical water tank with radius and height marked

A box's volume is base area times height. This tank's base is a circle. Same idea?

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Stack Up the Circular Discs

A stack of identical circular discs, each area pi r squared, rising to height h

Each disc has area . Stack of them, and the volume is .

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

The Cylinder Volume Formula Itself

Labeled cylinder showing radius r at the base and height h

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Cylinder Volume in a Direct Problem

A water tank has radius 5 ft and height 12 ft:

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

When the Diameter Is Given

A pool has diameter 16 ft and depth 4 ft. First, .

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Working Backward to a Radius

A container holds cm³ with height 20 cm. Find .

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Your Turn: A Small Cylinder

Find the volume of a cylinder with radius 3 cm and height 7 cm.

Leave your answer in terms of . Try it before advancing.

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

How Does a Cone Compare?

A cone has the same circular base and the same height as a cylinder.

How much of the cylinder's volume does it hold? Make a guess.

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Three Cones Fill the Cylinder

A cone inscribed in a matching cylinder, annotation that three cone-fuls fill the cylinder

It takes exactly three cone-fuls to fill the cylinder. So .

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Cone Volume in a Direct Problem

A cone has radius 5 cm and height 12 cm:

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

A Real-World Cone to Measure

An ice-cream cone has diameter 6 cm and height 13 cm. First .

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

The One-Third Has a Condition

The cone is one-third of the cylinder only when they share the same base and height.

With different dimensions, you must compute each volume separately.

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Compare Shapes With Different Sizes

Cone: , . Cylinder: , .

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Find a Cone's Radius From Its Volume

A cone has volume ft³ and height 18 ft.

Set up and solve for . No template — work it out.

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Two Cone Traps to Avoid

⚠️ The formula uses the radius — halve the diameter first
⚠️ Don't drop the one-third — three cones fill one cylinder

Grade 8 Math | 8.G.C.9
Volume Formulas | Lesson 1 of 2

Cylinder Is the Baseline; Cone Is a Third

✓ Cylinder: — a circle lifted to a height
✓ Cone: — one-third of the matching cylinder
⚠️ One-third holds only with the same base and height

Next: the sphere — a shape with no flat base at all.

Grade 8 Math | 8.G.C.9

Click to begin the narrated lesson

Know the formulas for the volumes of cones, cylinders, and spheres