We study the rho resonance using lattice QCD, employing a variational method. We scan the resonance region by varying the back-to-back momentum of the pions. To vary the pion momentum we use lattice geometries with one elongated spatial direction. For this study we use three different elongations, which allows us to scan finely the resonance region and compute the phase-shifts. The resonance mass and width are extracted from a fit at two different quark masses and the data is extrapolated to the physical point. I discuss the lattice results and compare them with predictions from different effective models.