Definition:
The total distance around the outside of a
rhombus

Try this
Drag any orange dot to resize the rhombus. The perimeter is calculated as you drag.

How to find the perimeter of a rhombus

Like any polygon, the perimeter is the total distance around the outside,
which can be found by adding together the length of each side.
In the case of a rhombus, all four sides are the same length by definition,
so the perimeter is four times the length of a side. Or as a formula:

In the figure above, drag any orange dot to resize the rhombus. From the side length shown, calculate the perimeter
and verify your result matches the formula at the top of the diagram.