A numerical multiplier defined by the geometrical spacings between electrodes, which is used in conjunction with the voltage-to-current (R) ratio measured in electrical resistivity surveys to give an apparent resistivity (ρ‎_a) such that ρ‎_a = K_g × R. The generalized formula for calculating K_g for a four-electrode configuration is: K_g = 2π‎(1/C₁P₁ – 1/C₁P₂ – 1/C₂P₁ + 1/C₂P₂)¹ where C₁ and C₂, and P₁ and P₂ are the current and potential electrode positions respectively. The geometric factor for the three main electrode configurations are: dipole–dipole, K_g = π‎n(n + 1)(n + 2)p; Schlumberger, K_g = (π‎p²/q)(1 – q²/4p²); Wenner, K_g = 2π‎p, where p and q are defined for each case.