The loss from multiple human blockers is empirically and analytically investigated at millimeter wave frequencies. Humans are modeled as absorbing screens of infinite height with two knife-edges, while physical optics is used to compute the contribution from rays diffracting around them. This model is validated with blocking gain measurements of multiple human blocking configurations on an indoor link. The blocking gains predicted from physical optics have good agreement with measurements ranging from -50 dB to 2.7 dB, making the absorbing screen model suitable for real human blockers. Mean and standared deviation of prediction error are approximately -1.2 and 5 dB, respectively.