Equivalent yardages (e) are used to compare the relative excavation costs of different materials (e.g., hard rock vs. loose topsoil). To use equivalent yards, a standard material (e.g., common soil) is given a unit value of e = 1.0. Materials which are more expensive to excavate have equivalent yardage values e > 1.0; materials which are less expensive to excavate have e < 1.0.

The idea is to create a scale to compare relative mining costs (i.e., how much does it cost to mine a cubic yard of hard rock vs. a cubic yard of weathered overburden).

Figure: Equivalent yards is a relative value used to make quick calculations about different mining costs that might be experienced across the mine property.