The experimental excited state dipole moment of N-nonyl acridine orange was determined using Bakhshiev's and Kawski–Chamma–Viallet's formulae and solvent polarity parameter proposed by Reichardt. These experimental results were completed with theoretical results using quantum chemical methods. The experimental (μexp = 10.76 D) and theoretical (μcal = 9.9 D) dipole moments in the ground and excited state () were compared.