A regular polygon with 7 sides is a heptagon.
To find the measure the interior angle (I):
Where n is the number of sides (7):
And the sum of the interior angles is:
The sum of the exterior angles (Se) is 360°.
And the sum of one exterior angle (E):
In summary:
Name: Heptagon
Sum of interior: 900°
1 Interior: 128.57°
Sum of exterior: 360°
1 Exterior: 51.43°