It is estimated that about 1 million Earths could fit inside the sun. The sun has a diameter that is about 100 times the diameter of the Earth. The sun is a sphere shape, so to determine how many Earths could fit inside, the difference in diameter has to account for three dimensions: from top to bottom, left to right, forward to backward and everywhere in between. Since 100 Earths could line up across the sun, this number is multiplied by itself three times — 100 x 100 x 100 — to calculate how many Earths could fit inside the sun.
More about the sizes of Earth and the sun: