Gaming miniatures are usually described as Xmm rather than 'X/Y(th)' as is used in scale modelling. The distance is from the base to the eyes on a normal human.
Current new models coming out for Wahammer Fantasy are 32mm Heroic scale. GW has been pushing up the scale of the game in recent years, ostensibly so that more detail can be fit onto plastic models. Older models, many of which are still the current sculpt that's for sale, are 28mm heroic.
'Heroic' just means that certain features, like heads and weapons, are not to scale with the body. This makes them look better and easier to recognize when viewed from comparatively far away on a gaming table. It does however make it hard to use parts from true-scale models, since a model that is the same height will look like it has a tiny head and twig for a weapon next to gaming models. If you do a straight conversion based on the model's height you will come out with approx. 1/56th for a comparable true scale model, but in reality that will look very silly and most people use more like 1/35th when incorporating true scale parts into a gaming army.