Formula

Base Times Height Method :
Area of Rhombus = b * h

Diagonal Method :
Area of Rhombus = ½ * d1 * d2 

Trigonometry Method :
Area of Rhombus = a² * SinA

Perimeter of Rhombus = 4(a)

where,
a = side, b = base, h = height, d1, d2 are diagonals