Approximately how much can a Sun-like star's radius increase upon entering the red giant phase?

Answer

By a factor of one hundred or more

The expansion during the red giant phase is massive, with the star often increasing its radius by a factor of 100 or greater.

Approximately how much can a Sun-like star's radius increase upon entering the red giant phase?

#Videos

Why Do Red Giant Stars Get Bigger? - YouTube

evolutionastronomystellarstarred giant