Question: How many atoms are in a full grown adult?

Robert Woolfson answered on 16 Mar 2015:

Alright, lets assume that a person is made completely of carbon because that makes doing all the calculations a bit easier. Twelve grams of carbon has about half a quadrillian atoms in (this is called Avogadro’s number, and it’s 6×20 to the power of 23), so a person weighing, say, 60 kg, would have three thousand quadrillion atoms (30,000 x10 to the power of 23).

That’s big number. I can’t think of any comparison to how big that is. Of course, we’re not made of pure carbon and the actual number will be a less than that as we’ve got all kinds of things in us, a lot of which weighs more than carbon. But hopefully that gives you some idea of how big numbers are when we talk about atoms.