Easy. Firstly calculate the total square metres of the concrete slab and then divide this figure by 12.5. This will give you the number of sheets required. (Calculation based on standard mesh sheet size of 6 metres x 2.4 metres)
Firstly calculate the total lineal metres. For a single layer of trench mesh, divide this figure by 5.5. You now have the total number of trench mesh (6 metre lengths) required for the job. If a double layer of trench mesh is required, then double this figure.