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Half cylinder calculator

Exactly half of a full cylinder — a semicircular trough or channel. Enter radius and length for the volume.

Troughs, channels and half-round tanks all use the half-cylinder shape, and this half cylinder calculator sizes them instantly: enter the radius or diameter and the length, and read half the full-cylinder volume.

How the calculation works

  1. Measure the radius (or diameter) of the semicircular end.
  2. Measure the length of the half cylinder.
  3. Work out the full-cylinder volume π r² h.
  4. Halve it — a half cylinder is exactly 50% of the full shape.

Worked example. Take a cylinder with a diameter of 10 cm (so a radius of 5 cm) and a height of 25 cm. The base area is π × 5² = 78.54 cm², and multiplying by the height gives a volume of about 1.96 litres (1,963 cm³ · 0.52 US gallons).

For anything that holds liquid, measure the inside of the cylinder — the wall takes up space that the contents cannot.

Every half cylinder page

Each page below targets a specific question and opens with the calculator ready to go:

Good to know

What is the formula for a half cylinder?
V = ½ π r² h — exactly half the volume of the full cylinder with the same radius and length.
Is a half cylinder the same as a semicircle?
A semicircle is the flat half-disc that forms the end; a half cylinder is that shape extended along a length, which is what gives it volume.

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