We present a simple parameterization of the running coupling constant α V (q), defined via the static potential, that interpolates between 2-loop QCD in the UV and the string prediction V (r) = σr − π 12r in the IR. Besides the usual Λ-parameter and the string tension σ, α V (q) depends on one dimensionless parameter, determining how fast the crossover from UV to IR behavior occurs (in principle we know how to take into account any number of loops by adding more parameters). Using a new ansatz for the lattice potential in terms of the continuum α V (q), we can fit quenched and unquenched Monte Carlo results for the potential down to one lattice spacing, and at the same time extract α V (q) to high precision. We compare our ansatz with 1-loop results for the lattice potential, and use α V (q) from our fits to quantitatively check the accuracy of 2-loop evolution, compare with the Lepage-Mackenzie estimate of the coupling extracted from the plaquette, and determine Sommer's scale r 0 much more accurately than previously possible. For pure SU(3) we find that α V (q) scales on the percent level for β ≥ 6.