• Question: How many molecules are in the human body?

    Asked by anon-244324 to Ondrej, Jordan, Ed on 20 Mar 2020.
    • Photo: Edward Banks

      Edward Banks answered on 20 Mar 2020:

      Very very roughly, somewhere in the order of 10^27; or 1000000000000000000000000000.

    • Photo: Ondrej Kovanda

      Ondrej Kovanda answered on 20 Mar 2020:

      Let’s make a quick and very rough estimate. Consider a 70 kg human. Now, humans are made of 60 percent of water. 0.6 times 70 kg is 42 kg of water. A single mole of water is 18 g, that is about 2333 moles, each of them contains 6.022 times 10^23 molecules. Therefore, only the water in the human body amounts for roughly 1.4 times 10^27 molecules. Now what about the rest? Most of the remaining 28 kg are made up of molecules much heavier than water – such as proteins, fat, sugars, … They will therefore be in much lower numbers than those of the water. Therefore, if we say there are order of 10^27 molecules in the human body, we are probably not completely wrong.

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