The human body is ____ percent water

How much of the human body is water?

Firstly, what about actual liquid water? There’s water in the blood plasma, and water in the protoplasm inside cells, and various other fluids in the body. How much is there as a percentage by weight or by volume? (contents of the stomach, intestines or bladder don’t count)

Secondly, there are more complex molecules such as proteins that contain hydrogen, oxygen and other elements. When a body is cremated, they break down into water and other stuff. How much water does a cremated body produce?

Depending on age and body mass composition the human body varies from 45% to 75% by weight. Since solutions take up less space than their separate parts of water and solute the percentage by volume will be higher.

9% of the body’s mass is hydrogen (An average of some sort of course, but it will vary less than the water content.)

Hydrogen is only 1/9th mass of water so if all the hydrogen became water cremating a body would create water equivalent to 81% of the original body mass. I’m sure though there are a lot of compounds that wouldn’t want to give up their hydrogen to oxygen, so that’s an upper bound.

Probably not. Elemental oxygen is one of the most reactive substances around. Given the choice between combining with oxygen and combining with almost anything else, almost everything will choose the oxygen.

It’s more like most compounds will want to give up their hydrogen for oxygen, making carbon dioxide … the loose hydrogen then takes up with oxygen to make water …

Oxygen is a powerful oxidizer …

While the history hasn’t been asked about, the famous determination of the water content in humans was by Francis Moore. There was a good article about him by Atul Gawande in the New Yorker back in May 2003.

I’m what they call a water man, Jack.

And if this ever weren’t true, you’re probably in very bad shape, because it means you have some fluorine in you.

You know what they put in children’s ice cream, Mandrake?

I meant “a lot” as in “many different”, not as in “a large percentage”, but on further thought I see that even that was wrong.

No fair username/post combo.

To be fair, fluorine in the form of sodium fluoride or other compounds used to prevent tooth decay is a very different thing from, say, hydrogen fluoride or diatomic fluorine. But I couldn’t help but play on the connection there, especially with my username :).