Tigers Panthera tigris continue to decline despite the best efforts of the worldwide scientific and conservation communities. Prey depletion has been linked to this decline, but a clear definition of what constitutes preferred prey and preferred prey weight range does not exist. This is critical information if we are to assess tiger reintroduction potential, monitor unforeseen poaching of predators and prey, and successfully conserve the species. Here we reviewed the available literature on tiger diet and prey availability and calculated Jacobs's electivity index scores from 3187 kills or scats of 32 prey species. We found that wild boar and sambar deer are significantly preferred by tigers, with red deer and barasingha likely to be significantly preferred also with a larger sample size. Prey body mass was the only variable that related to tiger prey preference with species weighing between 60 and 250 kg preferred by tigers yielding a ratio of predator to preferred prey of 1:1, which is similar to other solitary felids. This information can be used to predict tiger diet, carrying capacity and movement patterns, as it has been for Africa's large predator guild, and has important implications for tiger conservation throughout its distribution.