One variation of a method for quantifying user engagement includes: serving a digital advertisement to a mobile device; recording a first proportion of pixels of the digital advertisement rendered on a display of the mobile device during a first sampling period; recording a second proportion of pixels of the digital advertisement rendered on the display of the mobile device during a second sampling period offset in time from the first sampling period; calculating a cumulative pixel exposure of the digital advertisement at the mobile device based on a combination of a first product of the first proportion of pixels and a duration of the first sampling period and a second product of the second proportion of pixels and a duration of the second sampling period; and storing the cumulative pixel exposure as an engagement metric for a user consuming the digital advertisement at the mobile device.