VY Canis Majoris is the largest known star.
University of Minnesota professor Roberta M. Humphreys estimates the radius of VY CMa at 1,800 to 2,100 solar radii. To illustrate, if Earth's Sun were replaced by VY Canis Majoris, its radius might extend beyond the orbit of Saturn (about 9 AU). Assuming the upper size limit of 2100 solar radii, light would take more than 8 hours to travel around the star's circumference, compared to 14.5 seconds for the Sun. It would take 7×1015 Earths to fill the volume of VY Canis Majoris.
If the Earth were to be represented by a sphere one centimeter in diameter, the Sun would be represented as a sphere with a diameter of 109 centimeters, at a distance of 117 meters. At these scales, VY Canis Majoris would have a diameter of approximately 2.3 kilometers, assuming the upper limit estimate of its radius.