Endo-View · Simulations
The size comparer
A hair, an egg, a blood cell, a bacterium and a virus are all drawn here at true scale, on one scale bar. Drag the zoom to go from a hair to a virus, or pick one to bring it to the middle. At every zoom, whatever is too big runs off the edge and whatever is too small is a speck.
Drag to turn it, scroll or pinch to zoom, right-drag or two fingers to move, the arrows (or the arrow keys) to go to the next thing. Its zoom and the bars’ zoom are the same.
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Its width, without its clear shell (the zona, which adds about 16 µm all round) or the cells around it. Just visible to the eye, like a full stop. between 110 and 120 µm Smaller than a pixel at this zoomRuns off the edge
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Its width. Hairs run from about 50 to 100 µm, and differ from person to person. between 50 and 100 µm Smaller than a pixel at this zoomRuns off the edge
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Its length, head and tail. The head alone is about 4 µm. between 50 and 60 µm Smaller than a pixel at this zoomRuns off the edge
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Its width: a disc, about 2 µm thick. between 6 and 8.2 µm Smaller than a pixel at this zoomRuns off the edge
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Its length: a rod about 0.5 µm wide. Bacteria differ a great deal in size. between 1 and 3 µm Smaller than a pixel at this zoomRuns off the edge
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Its width. Viruses are the smallest of these: some are a third of this, some twice as big. between 60 and 140 nm Smaller than a pixel at this zoomRuns off the edge
Drag, or use the arrow keys
How many times
- A hair is about 700 viruses wide.
- About 15 red blood cells fit across a human egg.
- A sperm cell is about 7.3 red blood cells long.
- About 3.8 bacteria laid end to end span a red blood cell.
- About 20 viruses fit across a bacterium.
What is drawn, and what is real
The lengths are real and to scale. The shapes are simple bars: the colours and the forms are drawn, not photographed.
Each size is the one people usually mean: a hair’s width, a cell’s width, a sperm cell’s length. Real ones vary, so every size is shown with its range.
The numbers for the egg and the sperm cell are the same as in the journey to life, chapters 4 and 5.
Where the sizes come from
- Hair: “Diameter of a human hair”, The Physics Factbook (hypertextbook.com), a collection of measurements from the literature.
- Egg cell and sperm cell: the journey to life, chapters 4 and 5 (see How we know).
- Red blood cell: Hoffbrand A.V. and Moss P.A.H., Essential Haematology: a disc about 7 to 8 µm across.
- Bacterium: Milo R. and Phillips R., Cell Biology by the Numbers (2015): E. coli is about 2 µm long and 0.5 to 0.8 µm wide.
- Virus: Zhu N. et al., “A novel coronavirus from patients with pneumonia in China, 2019”, New England Journal of Medicine 382 (2020): 60 to 140 nm across.