Stars exist that are both bigger and smaller than the sun. The sun has a radius of 1.4 million kilometers and, relative to other stars, is an average size.
As of 2014, the biggest known star is VY Canis Majoris, estimated to be 1540 times the size of the sun. The smallest known star, OGLE-TR-122b, has a radius of 167,000 kilometers. The biggest stars, called red giants, are thought to be around 1500 times the size of the sun. The smallest stars, known as red dwarfs, have around 10 percent of the mass of the sun. The sun is a yellow star, and as of 2014, the largest known yellow star is HR 5171 A in the Centaurus constellation, at 1300 times the size of the Sun.