Calculate the size of the interior angle of a regular hexagon close hexagon A polygon with six sides.. Show answer Hide answer. The sum of interior angles is \((6 - 2) \times 180 = 720^\circ\).

As we know, the exterior angle plus the interior angle adds up to 180°, so the missing angles moving clockwise from the top are: 180 – 71.4 = 108.6° 180 – 56.4 = 123.6° ...