How big is the Sun? The Sun is really big. Find out how big the sun is. You see the Sun almost everyday, but do you know how big the Sun is? There are many ways of answering that question. First the numbers: The Sun's diameter is about 870,000 miles and the Sun's radius is about 435,000 miles. Based on this information, you can calculate the circumference, volume, and surface of the Sun and get the following information: Sun Circumference: 2,700,000 miles Sun Surface: 2,380,000,000,000 square miles Sun Volume: 345,000,000,000,000,000 cubic square miles The above are just numbers, and they are so big that they don't really tell you much. Sort of like the US debt! Anyway, if we compare them to Earth you may gain a better perspective. The Sun's circumference (distance around at equator) is about 2,700,000 miles compared to Earth's 25,000 miles. That means the Sun's circumference is about 108 times larger than Earth's. The Sun's surface area is about 2,380,000,000,000 square miles and Earth's surface area is about 200,000,000 square miles. Thus, the real estate on the Sun is about 11,900 times larger than Earth in square miles. Finally, which is the most telling how big the Sun really is, the Sun's volume is 345,000,000,000,000,000 compared to Earth's volume, which is 260,000,000,000. That means that the Sun is 1,300,000 times bigger than earth in cubic square miles. That is huge!