How Do You Find the Area of a Quadrilateral?
To find the area of a quadrilateral, find the height and width of the shape (for rectangles, squares, parallelograms and trapezoids), and then multiply the two numbers together. For rhombuses and kites, find the length of the diagonals, multiply the diagonals, and divide by two. Express the result in square units.

Find the height and width of the quadrilateral
For a square and a rectangle, identify the length of the base and one side. For a parallelogram, find the vertical height from the base to its parallel side. For a trapezoid, add the two parallel sides together to get the width and divide by two, then find the vertical height between those two sides.

Find the diagonals for other quadrilaterals
For quadrilaterals such as a rhombus and a kite, find the diagonals. Identify the diagonals as the measurements between both sets of opposite angles.

Multiply the two numbers and divide if necessary
Multiply the height and width together for rectangles, squares, parallelograms and trapezoids. For rhombuses and kites, multiply the measurements of the two diagonals, and then divide by two.

Express the area in square units
Always express the area of the quadrilateral in square units of the measurements of the width and height or the two diagonals.