Comparing the Size of Earth vs. the Sun One of the most astonishing facts in astronomy is the vast difference in size between Earth and the Sun. This comparison helps us understand the scale and enormity of celestial bodies in our solar system. Earth's Size: Diameter: Earth's diameter is about 12,742 kilometers (7,918 miles). Volume: Earth's volume is approximately 1 trillion cubic kilometers (260 billion cubic miles). Sun's Size: Diameter: The Sun's diameter is about 1,391,000 kilometers (864,0