Chain Link Mesh is measured diagonally in both directions using inside measurements. Sometime the two measurements will not be the same. This depends on who manufactured the chain link and the location where you purchased it from.
The most common mesh sizes for chain link fence are 2" (typically 9 or 11 gauge wire) and 2-1/4" or 2-3/8" (typically 11-1/2, 12 or 12-1/2 gauge wire).
Two inch mesh chain link is the best because you can use almost all of our fence slats. Your options are wide open.
If your mesh size is 2-1/4 or larger your options are limited. Usually 2-3/8" and 2-1/2" mesh chain link fabric is made from 11-1/2, 12-1/2 or 13 gauge wire. The higher the gauge number the thinner the wire. Also with larger mesh sizes the framework (top rail, posts, etc.) is usually not strong enough to support heavy windloads. If there was a fence slat on the market that provided full privacy for 2-1/2" mesh, a strong wind would most likely blow the fence over. Then again, it also depends on the soil conditions, height of fence, how deep the posts are in the ground and how much cement was used to install the fence post. We have a lot of people that are frustrated because they install their fence they purchased from a box store and find out they can't use a full privacy slat because their chain link mesh is to large. A lot of box stores don't even sell 2" mesh.