The International Astronomical Union (IAU) names 88 constellations of stars. In the table below, they are ranked by the solid angle that they subtend in the sky, measured in square degrees and millisteradians.
These solid angles depend on borders between the constellations: the list below is based on constellation borders drawn up by Eugène Delporte in 1930 for the IAU and published in Délimitation scientifique des constellations (Cambridge University Press). Before Delporte's work, there was no standard list of the borders of each constellation.
Delporte drew the borders along vertical and horizontal lines of right ascension and declination; however, he did so for the epoch B1875.0, which means that due to precession of the equinoxes, the borders on a modern star map (e.g., for epoch J2000) are already somewhat distorted and no longer perfectly vertical or horizontal. This distortion will increase over the centuries to come. However, this does not change the solid angle of any constellation.