•Assessed daily-life mind wandering (MW) with dichotomous and continuous probes.•Estimates of daily-life MW varied dramatically depending on the probe used.•Results indicate that seeking a single value for MW is not very psychologically informative. Recent claims that people spend 30–50% of their waking lives mind wandering (Killingsworth & Gilbert, 2010; Kane et al., 2007) have become widely accepted and frequently cited. While acknowledging attention to be inconstant and wavering, and mind wandering to be ubiquitous, we argue and present evidence that such simple quantitative estimates are misleading and potentially meaningless without serious qualification. Mind-wandering estimates requiring dichotomous judgments of inner experience rely on questionable assumptions about how such judgments are made, and the resulting data do not permit straightforward interpretation. We present evidence that estimates of daily-life mind wandering vary dramatically depending on the response options provided. Offering participants a range of options in estimating task engagement yielded variable mind-wandering estimates, from approximately 60% to 10%, depending on assumptions made about how observers make introspective judgments about their mind-wandering experiences and how they understand what it means to be on- or off-task.