One way to measure the complexity of a smooth manifold is by considering the minimal volume MinVol introduced by Gromov, which is simply defined as the infimum of the volume among metrics with sectional curvature between -1 and 1. I will introduce a close variant of MinVol, called the essential minimal volume, which has some advantages: it is always achieved by Riemannian metrics and it can be estimated for Einstein 4-manifolds and most complex surfaces in terms of topology.