Calculate total time for a TV series.
Total watch time is episodes times episode length, but the intro-skip figure is worth separating out because it compounds surprisingly hard: a 45-second intro across 50 episodes is over half an hour. Converting the total into three-hour evenings turns an abstract hour count into something you can actually plan around.
Episodes
seasons x episodes per season
Watch time
episodes x episode minutes - episodes x skip seconds / 60
Yes, proportionally. Watching at 1.25x cuts the total by 20%, since time scales inversely with speed.
Because 37 hours is hard to picture, while twelve evenings tells you whether it fits before a series finale you are trying to catch up for.