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Geometry

Volume of a cylinder

The area of the circular base times the height.

V=πr2h

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r = 3h = 10
  • Volume = πr²h = 282.74
  • Surface area = 2πr² + 2πrh = 56.549 + 188.5 = 245.04

What the symbols mean

V
the volume
r
the radius of the circular end
h
the height (or length) of the cylinder

When to use it

Use it for cans, pipes, tanks, glasses and columns. For a pipe or a tube, subtract the inner cylinder from the outer one. Solve for h to see how full a cylindrical tank is from the volume poured in.

Worked example

A can has a radius of 3 cm and a height of 10 cm. What is its volume? (r = 3, h = 10)

  1. Start from the formula.

    V=π⁢r2⁢h
  2. Substitute r = 3, h = 10 and work it out.

    V=π·32·10
    =π·9·10
    ≈282.743

Answer V ≈ 282.74 cm³, about 283 ml

Why it works

A cylinder is a stack of identical circles. Its volume is base area times height, like any prism: πr2×h.

Common mistakes

  • Using the diameter as r, which gives four times the volume.
  • Using 2πrh, which is the curved surface area, not the volume.