What is the approximate diameter of the Sun?

What is the approximate diameter of the Sun? The Sun’s diameter is approximately 1.39 million kilometers. That is the distance across the Sun measured through its center, using the visible photosphere as the practical boundary.

Astronomers commonly express the Sun’s size through its radius, which is about 695,700 kilometers. Doubling that radius gives a diameter of roughly 1,391,400 kilometers, so “1.39 million km” is an appropriate rounded answer. The exact measured value varies slightly because the Sun has no solid surface and its outer atmosphere fades gradually into space.

The Sun is about 109 times wider than Earth. It is also vastly more voluminous: roughly 1.3 million Earths could fit inside it if they were rearranged to fill the available space. Despite its enormous size, the Sun is an ordinary-sized star compared with red supergiants and other giant stars.

The Sun’s apparent width in Earth’s sky is about half a degree because it is also extremely far away. Its average distance from Earth is about 149.6 million kilometers, or one astronomical unit. Sunlight takes about 8 minutes 20 seconds to travel that distance.