Methods, apparatus, and systems are disclosed for estimating audience exposure based on engagement level. An example apparatus includes at least one memory, machine readable instructions, and processor circuitry to at least one of instantiate or execute the machine readable instructions to identify a user activity associated with a user during exposure of the user to media based on an output from at least one of a user device, a remote control device, an image sensor, or a motion sensor, classify the user activity as an attention-based activity or a distraction-based activity, assign a distraction factor or an attention factor to the user activity based on the classification, and determine an attention level for the user based on the distraction factor or the attention factor.