In the Standard Model, partial unification of the non-Abelian running gauge couplings is achieved at the scale ${\mu }_{32}^{\mathrm{SM}}\approx 2.8\times {10}^{16}\mathrm{GeV}$. Elaborating on this fact, we discuss a simple general parametrization for the new physics corrections leading to full unification at some scale $M_X$. We show that for any new physics model such that the corrections to the non-Abelian couplings are equal (or nearly so), $M_X$ is equal (or close to) the partial unification scale ${\mu }_{32}^{\mathrm{SM}}$; the latter scales could be disentangled only if the corrections to the non-Abelian couplings are significantly different. We explore how the parametrization works for some relevant models with new physics below $M_X$, as low-energy supersymmetry, split supersymmetry, etc. As for models with a desert up to $M_X$, we explore, in particular, how the parametrization works for string-inspired corrections; we find a phenomenologically remarkable possibility for unification at about 100 TeV, suggesting a low string scale, in addition to the more conservative possibility for unification at ${\mu }_{32}^{\mathrm{SM}}$; for models with power-law running/threshold corrections, we also outline an interesting connection with the number of fermion families propagating in the bulk.

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• Grand unified models
• Renormalization group
• String phenomenology