How many atoms are there in a grain of sand?

Avogadro tells us that we have 6.023 x 10^23 SiO2 units per gram, so there would be 6.023 x 10^23 / 60 ≈ 1 x 10^22 SiO2 units in a gram of pure SiO2, and with SiO2 composed of 3 atoms, that puts us at 3 x 10^22 atoms per gram of SiO2. Now, a grain of sand does not weigh 1 gram. It weighs less. read more

One grain or sand is therefore 1.83 x 10^-4 moles of sand. Using Avogadro’s number, we can then determine that there are 1.10x10^20 molecules in a single grain of sand. If you want atoms, then there are three atoms per molecules, so you multiply that number by 3 to get 3.31 x 10^20. read more

According to Jason, there about 700 trillion cubic meters of beach of Earth, and that works out to around 5 sextillion grains of sand. Jason reminds us that his math is a rough estimate, and he could be off by a factor of 2 either way. So it could be 2.5 sextillion or there could be 10 sextillion grains of sand on all the world’s beaches. read more