Angular Size Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026Why the Moon and Sun look almost exactly the same size
Angular size describes how large an object appears from a given viewpoint, independent of its actual physical size - a small nearby object and a huge distant one can share the exact same angular size.
Worked example
For the Moon (3,474 km diameter) at its average distance of 384,400 km:
Angular Size = 2 x arctan(3474 / (2 x 384400)) = 31.068 arcminutes (0.517805 degrees)
This result matches the Moon's real average angular size of about 31 arcminutes - remarkably close to the Sun's own angular size (also about 31-32 arcminutes), despite the Sun being roughly 400 times larger in true diameter, simply because it is also roughly 400 times farther away. This near-perfect coincidence is exactly why total solar eclipses are possible.