Scale Explorer

Microscopic

How big is a paramecium?

Paramecium · Range across the genus, which includes P. caudatum · Paramecium

Length
0.05–0.32 mm 0.002–0.013 in range
Show
Red blood cell, Paramecium, Human hair (width), Human drawn to the same scaleRed blood cell: diameter 7.5–8.7 µm (too small to see at this scale). Paramecium: length 0.05–0.32 mm (too small to see at this scale). Human hair (width): average diameter ≈ 70 µm (too small to see at this scale). Human: height 1.61–1.75 m.Red blood cell: 7.5–8.7 µm (too small to see at this scale)Paramecium: 0.05–0.32 mm (too small to see at this scale)Human hair (width): ≈ 70 µm (too small to see at this scale)Human: 1.61–1.75 mHuman1.61–1.75 mRed blood cell7.5–8.7 µm · too small to seeParamecium0.05–0.32 mm · too small to seeHuman hair (width)≈ 70 µm · too small to see

Red blood cell, Paramecium and Human hair (width) are too small to see at this scale and are marked with ▲.

Everything is drawn to the same scale, standing on the same ground line. Silhouettes are simplified outlines scaled to the measured dimension. A faded outline shows the top of a size range.

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Dimensions

MeasurementMetricImperialNotesSource
Length 0.05–0.32 mm 0.002–0.013 in Length range across the genus (0.002 to 0.013 inch). Range: varies [1]

About the paramecium

Paramecium is a genus of single-celled, free-living protozoans that is widely used as a model organism because it is easy to grow in the laboratory. The cell is an elongated oval covered in beating cilia, which it uses both to swim and to sweep bacteria and other food into its mouth. Depending on the species, paramecia range from about 0.05 to 0.32 mm long.

  • Paramecia have two kinds of nucleus: a large macronucleus that runs the cell's metabolism and at least one small micronucleus that holds the germline genetic material. [1]
  • Paramecium is the only genus in the family Parameciidae, within the ciliate phylum Ciliophora. [1]

How many fit?

  • ≈ 5,000–35,000 × Paramecium · length lined up end to end match the Human · height
  • ≈ 5.7–43 × Red blood cell · diameter lined up end to end match the Paramecium · length

Counts divide one sourced figure by another. "End to end" uses each object's main measurement; weight and volume rows appear only when both figures are sourced.

How it compares

  • 5.7–43× A paramecium is about 5.7–43 times as long as a red blood cell is across. See side by side
  • 0.7–4.6× A paramecium is roughly as long as the width of a human hair is wide: between 0.7 and 4.6 times, depending on size. See side by side
  • 0–5.1× A paramecium is roughly as long as a grain of sand is wide: between 0 and 5.1 times, depending on size. See side by side
  • 1/11–100 A black garden ant is about 11–100 times as long as a paramecium. See side by side
  • 1/21–150 A grain of rice is about 21–150 times as long as a paramecium. See side by side
  • 1/5,000–35,000 An average adult is about 5,000–35,000 times as tall as a paramecium is long. See side by side

Factors compare the length of a paramecium with each object’s own main measurement (height for a human). Where a size varies, the factor is given as a range.

Notes on these figures

  • No primary or university source giving a length range specifically for P. caudatum could be fetched, so the range covers the whole genus.
  • No sourced width, mass or volume was found.

Sources

  1. Encyclopaedia Britannica, Paramecium. Accessed 25 September 2026.

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