For clients, usually agencies, that want viewability measurements see below on the report we ran May 2017 for Harley-Davidson. this report has both viewability and video play metrics.
For more details on the definitions and standard for viewability: https://support.digitalthrottle.com/hc/en-us/articles/115007128348-IAB-Measurements
The Report Explained
(1) The ad server impressions we use for billing and to compare to the client's third-party impressions like normal
(2) The number of impressions that could actual be measured. The math of (2) / (1) is column (3) the "viewability measurement rate"
(3) The ratio of impressions that were actually capable of being measured; math of (2) / (1)
(4) The ratio of videos played that were measured. It's based on column (2). So in this case, 83.2% is Viewable. Thus total impressions viewed is (4) x (2).
Total Video Plays served: 9,922
Total Video Plays capable of being measured (3) x(1) = (2): 9,313
Of this number, how many are "in view": (2) x (4) = 7,748
Total Video Plays that are unknown viewable: (1) - (2): 609
(5) The number of viedeo plays (1) that watched at least 75% of the video ad. AppNexus doesn't calcuated a 75% completion rate, so you'd use: (5) / (1) = for the 75% completion rate. In this case it's 4,842 / 9,922= 48.8%