Grains of sand come in all shapes and sizes, but the most common size is about a half millimeter across. You could put 20 grains of sand packed in side-by-side to make a centimeter, 400 grains would make one square centimeter, and 8,000 grains could fit into one cubic centimeter. By extension, this means that an astounding 1,888,000 grains of sand would fit into a single cup - which is definitely more than I would have guessed.
If our sun and all the other stars in our universe were the size of a grain of sand, all the stars in our galaxy would fill an Olympic-sized swimming pool.
If our galaxy were a grain of sand, the galaxies would fill several olympic-sized swimming pools.
We know there are 100 to 400 billion stars in the Milky Way and more than 100 billion galaxies in the Universe — maybe as many as 500 billion. If you multiply stars by galaxies, at the low end, you get 10 billion billion stars, or 10 sextillion stars in the Universe. At the high end, it’s 200 sextillion.