Abstract: The perceptual features of criminal penalties are crucial to their capacity to deter, at least in theory. This chapter devotes attention to the accuracy of people’s perceptions about criminal penalties. The empirical findings from so-called perceptual calibration studies are summarized, focused on people’s understanding of the statutory applicability of criminal sanctions, as well as the certainty and severity of punishments applied in practice. While the average citizen is reasonably well informed about what criminal penalties are statutorily allowed, he or she does a poor job estimating the probability and magnitude of the penalties. On the other hand, studies which inquire about more common offenses (alcohol and marijuana use) from more crime-prone populations (young people, offenders) reveal that perceptions are consistently better calibrated to actual punishments.