This is how to calculate the area of a rhombus. A rhombus is a quadrilateral shape in which all sides are congruent. A rhombus has two sets of parallel lines, the diagonals of which form 90-degree angles at the point they meet. Also the angles opposite to one another are congruent. The area of a rhombus can be gotten by multiplying both the diagonals and then dividing the total by 2. Say one of the diagonals is 10 and the other is 12, the area will be 10 x 12 = 120/2 = 60. That is how to calculate the area of a rhombus.