The Lesson
A paralleogram is a four sided shape with opposite sides parallel and equal in length.Dictionary Definition
The Oxford English Dictionary defines a parallelogram as "a foursided plane rectilinear figure whose opposite sides are parallel; especially one whose sides do not intersect at right angles."Properties of Parallelograms

Opposite sides of a parallelogram are parallel.

Opposite sides of a parallelogram are of equal length.

Opposite angles of a parallelogram are equal.

Adjacent angles of a parallelogram add up to 180°. They are supplementary angles.

All angles of a parallelogram add up to 360°.

The diagonals of a parallelogram bisect each other. The diagonals cross each other halfway along their lengths.
The Perimeter of a Parallelogram
The perimeter of a parallelogram is given by the formula:In this formula, b is the length of the base and s is the length of the side of the parallelogram.
The Area of a Parallelogram
The area of a parallelogram is given by the formula:In this formula, b is the length of the base and h is the height of the parallelogram.
Read more about how to find the area of a parallelogram
Interactive Widget
Here is an interactive widget to help you learn about parallelograms.What's in a Name?
Parallelogram comes from the Greek word "parallelogrammon" meaning 'parallel sides'.A Parallelogram is a Polygon
A parallelogram is a type of polygon. A polygon is a 2dimensional shape with straight sides. A parallelogram is an irregular polygon. Irregular polygons have different length sides and different angles.A Parallelogram Is a Quadrilateral
A parallelogram is a quadrilateral. A quadrilateral is a foursided polygon. Squares, rectangles and trapezoids are also quadrilaterals.Interior Angles of a Parallelogram
A parallelogram is a foursided polygon. The sum of the interior angles of an nsided polygon is is:
(n − 2) × 180°
This means the interior angles of a quadrilateral (where n = 4) add up to:
(4 − 2) × 180° = 360°
This is the case for all quadrilaterals, such as squares, rectangles and trapezoids.