Yet another method called the harmonic oscillator model of aromaticity (HOMA) is defined as a normalized sum of squared deviations of bond lengths from the optimal value, which is assumed to be realized for a fully aromatic system. An aromatic compound has HOMA value 1 whereas a non-aromatic compound has value 0. For all-carbon systems, the HOMA value is defined as:
where V=257.7 Å is the normalization value, n is the number of carbon–carbon bonds, and d are bond lengths (d=1.388 Å is the optimum value and d are the observed or computed values).