The Kirchhoff sum index KfS is a graph index defined for a graph on n nodes by KfS = 1/2 sum_(i = 1)^n sum_(j = 1)^n (Ω)_(i j)/(d)_(i j), where (Ω)_(i j) is the resistance distance matrix and (d)_(i j) is the graph distance matrix. Unless otherwise stated, hydrogen atoms are usually ignored in the computation of such indices as organic chemists usually do when they write a benzene ring as a hexagon. Precomputed values for many graphs are implemented in the Wolfram Language as GraphData[g, KirchhoffSumIndex].

Balaban index | graph distance matrix | Kirchhoff index | resistance distance