To achieve maximum strength and durability in a concrete pad, it should be reinforced. When placed within the framework of the concrete forms prior to pouring the pad, wire mesh has proven to be an effective reinforcing material. Along with accurately estimating the quantities of concrete, forms, tools and labor for a project, it is also important to be able to calculate the amount of wire mesh needed.

Calculate the rectangular area of the pad. Measure the length in feet of one of the sides of the area that the concrete pad is to cover. Call this value "L1."

Measure the side that is the directly next to and perpendicular to the side measured in Step 1. Call this value "L2."

Multiply the measurements from Step 1 and Step 2 together. This resulting number is the area ("A") in square feet of the concrete pad:
A = L1*L2 
Divide the area number calculated in Step 3 by 5, as wire mesh in most commonly sold by the linear foot, in 5foot wide rolls. This will give you the number of linear feet of mesh needed. Call this value "f."
A/5 = f
Find out how long the rolls of mesh are that are sold in your area. Divide "f" by this number, and you have the number of rolls of mesh that you will need for the concrete pad.
Tips & Warnings
 To calculate the area for more complicated shapes of concrete pads, divide the shape up into smaller rectangular shapes and then add these areas together. You can also use an online calculator (see link in Resources).
References
 Photo Credit images.pennnet.com