What is the Sun's radius in kilometers?

The Sun’s radius is approximately 695,700 kilometers.

This is the nominal solar radius, a standardized value used by astronomers when comparing stars and other objects with the Sun. It is equal to 695,700 km, or 6.957 × 10^8 meters. The Sun’s diameter is therefore about 1,391,400 km—roughly twice its radius.

The number is a useful standard rather than a perfectly exact measurement of a sharply defined edge. The Sun is gaseous, and its visible surface is the photosphere, where the optical depth reaches about two-thirds. Different measurement methods and definitions of the photospheric boundary produce slightly different results.

The radius is also easy to confuse with other familiar solar distances. Earth is about 149.6 million km from the Sun on average, while 6371 km is approximately Earth’s mean radius. The Sun’s radius is about 109 times Earth’s equatorial radius and about 10 times Jupiter’s average radius.