Netflix viewers were hooked after three episodes of sci-fi drama Stranger Things and four episodes of true crime series Making A Murderer, according to analysis by the streaming service.
More than two thirds of UK fans (70%) who made it to that point in the show finished the series, Netflix found.
The third episode of Stranger Things saw Nancy look for Barb while Joyce became increasingly convinced her missing son Will was trying to talk to her.
The service analysed viewer data to find out at what point someone becomes likely to finish at least the first series of a show.
The "hooked findings" showed it took three episodes of Baz Luhrmann's hip hop show The Get Down to draw viewers in, four episodes of Aziz Ansari's Emmy-winning Master Of None, four of drug thriller Narcos and seven of mother-daughter drama Gilmore Girls.
It took six episodes of Jane The Virgin for fans to commit to powering through series one and four episodes of Marvel's Jessica Jones and French political drama Marseille.
There were no shows where viewers were sold on just the first episode alone.
Cindy Holland, vice president of original content at Netflix, said: "We've always known there is a commonality to great stories.
"The internet allows us to share these stories with audiences wherever they may be and what we see from the data is how similar our members watch and respond.
"The hooked findings give us confidence that there is an appetite for original and unique content, which is why we're excited to deliver variety in stories to our members - whether they're political dramas from France or musical dramas from the Bronx."
Last year's Netflix data showed Breaking Bad lured in an audience after two episodes, political drama House Of Cards won people over after three episodes, while superhero show Daredevil needed five.