The description for a photo on Nov 27th says that it was eight times the volume of the sun. Keep in mind, that is volume not diameter.
"Going, going, but not quite gone... Compare how Comet Holmes has increased in size and decreased in brightness in these two identically scaled images. Holmes was as voluminous as the sun in the November 11 image, but eight times the volume in the November 27 photo. Canon D40 images."