The members of the sartorite homologous series are complex sulfides Me2+8N–16–2XMe3+16+XMe+XS8N+8 where Me2+ is Pb and Me3+ is As and Sb, whereas Me+ is Ag and/or Tl. This paper presents calculation formulae for the homologue order N and for the separate substitution percentages for Tl + (As,Sb) ↔ 2Pb and Ag + (As,Sb) ↔ 2Pb substitutions. This enables one to evaluate the crystal chemistry and build a systematic classification of the sartorite homologues.