|Interior angle||128.571°||Like any regular polygon, to find the interior angle we use the formula (180n–360)/n . For a heptagon, n=7. See Interior Angles of a Polygon|
|Exterior Angle||51.429°||To find the exterior angle of a regular heptagon, we use the fact that the exterior angle forms a linear pair with the interior angle, so in general it is given by the formula 180-interior angle. See Exterior Angles of a Polygon|
|Where S is the length of a side. To find the exact area of a heptagon or any polygon, using various methods, see Area of a Regular Polygon and Area of an Irregular Polygon|
|Number of diagonals||14||The number of distinct diagonals possible from all vertices. (In general ½n(n–3) ). In the figure above, click on "show diagonals" to see them. See Diagonals of a Polygon|
|Number of triangles||5||The number of triangles created by drawing the diagonals from a given vertex. (In general n–2). In the figure above, click on "show triangles" to see them. See Triangles of a Polygon|
|Sum of interior angles||900°||In general 180(n–2) degrees . See Interior Angles of a Polygon|
Heptagons are not seen much in everyday life except in the UK, where there are coins in the shape of a heptagon.
On the right is the 50 pence coin. It is not a strict heptagon because the sides are actually curved arcs instead of straight lines.
The resulting shape is known as an "Equilateral Curve Heptagon".
It has one very curious property; in spite of not being a circle it has the same diameter everywhere! This is done so that it will always fit in coin-operated machines, but still feel different in the hand from other round coins - a help to sight-impaired people.