Studyfin Studyfin ✨ Sign up free

Volume

Grade 8 · Math · Free lesson

Hey there! Ready to explore 3D space? Let's learn how we measure the room inside three-dimensional shapes!

Have you ever wondered how much water fits inside a bottle, or how many toys can pack into a box? That's what volume is all about! While area measures flat 2D space, volume measures the actual 3D space an object occupies.

geometry

In grade 8 we go past boxes to curved solids. A cylinder is really a circular base stacked h units tall, so its volume is V = πr²h, where r is the radius of that circular base.

1 unit³

Cones and spheres follow from the cylinder. A cone with the same base and height holds exactly one third as much, V = (1/3)πr²h, and a sphere with radius r has volume V = (4/3)πr³.

Length (l) Width (w) Height (h) Volume = l × w × h
✏️ Worked example

Find the volume of a cylindrical soup can with a radius of 3 inches and a height of 12 inches. Use π ≈ 3.14.

  1. Identify the formula for the volume of a cylinder: Volume = πr²h.
  2. Plug in the given dimensions: radius = 3 in and height = 12 in.
  3. Square the radius first: 3² = 9.
  4. Multiply by π and the height: 3.14 × 9 × 12 ≈ 339.12.
  5. Write your final answer with cubic units: about 339.12 cubic inches (or 339.12 in³).
board
Want the full interactive lesson — quiz, animations, and Finn cheering them on?

More Math lessons