Rsun
solar radius
The solar radius is 695,700 kilometres, the IAU 2015 nominal value, fixed by resolution so that stellar parameters quoted in solar units do not shift every time the sun is remeasured. Stellar radii are almost always given in these units: a red dwarf is about 0.2 R☉, a red giant tens to hundreds.
Watch out: The sun has no surface, so the radius is defined at the photosphere, where the optical depth reaches a set value. Because that boundary is a convention, the IAU fixed the number rather than leaving it to drift, and older literature using 6.96 × 10⁸ m differs by a fraction of a percent.
| 1 Rsun | 695,700,000 m |
Solvers that use length