Viruses, Bacteria, Protists, and Fungi

What is the average size of a virus?

The smallest viruses are about 17 nanometers in diameter, and the largest viruses are up to 1,000 nanometers (1 micrometer) in length. By comparison, the bacterium Escherichia coli is 2,000 nanometers in length, a cell nucleus is 2,800 nanometers in diameter, and an average eukaryotic cell is 10,000 nanometers in length.

Virus Size (in nanometers)
Smallpox 250
Tobacco mosaic 240
Rabies 150
Influenza 100
Bacteriophage 95
Common cold 70
Polio 27
Parvovirus 20


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