Question: how many atoms are there in the entire world

Andrew McDowall answered on 30 Mar 2026:

We can’t count them precisely but we can take a rough guess.
The mass of the earth is pretty well known, around 5.972×10^24 kg. It’s composition is around 32.1% iron, 30.1% oxygen, 15.1% silicon and 13.9% magnesium plus a bunch of other elements in smaller amounts (we’ll ignore these). The atomic weight of these 4 elements are around 56, 16, 28 and 23.3, so, with the weights, the formula unit of a molecule of “earth” is something like 1 Iron to 1 Magnesium to 0.94 Silicon to 3.3 oxygen and weighs about 159.4 atomic mass units. Avogradro’s number. 6.022×10^23 gives us the number of entities in a gram equivalent to Avogradros number, called a mol.
So the if the mass of the earth is 5.972×10^24 kg,
that’s 5.972×10^27g.
divide by the molar mass to get the number of mols = 3.746 x10^25,
multiply by Avogradro to get the number of formula units = 2.256×10^49
and finally by the number of atoms within the formula unit (6.22) = 1.40×10^50 atoms

Maths was always a bit of weakness for me, but if I’ve got it right then there’s roughly 1,400,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 atoms in the world