Netflix knows your TV relationship status.

New data from the streaming-video service reveal the point at which users fully committed to some of the most popular TV shows on Netflix. For instance, it took only two episodes of “Breaking Bad” for the vast majority of viewers to buy into the crime drama and complete the first season. “How I Met Your Mother,” on the other hand, was a more acquired taste: The high-concept sitcom didn’t hit a critical mass of loyal Netflix viewers until its eighth episode.

Netflix examined viewing patterns in the first season of 25 of the most-watched TV series in its catalog, including its own original series like “House of Cards” and “Orange Is the New Black.” The company identified the episode where 70% or more of viewers went on to finish at least the show’s first season.

Netflix uses such data, including the popularity of certain subjects and actors, to predict viewing patterns and determine how much money to spend on original or licensed shows. Netflix Chief Content Officer Ted Sarandos says these statistics do not influence creative decisions about the company’s original series.

The rare glimpse into the Netflix viewing patterns reflects the kind of commitment issues TV fans are dealing with amid a deluge of programming.

There will be an estimated 400 scripted TV series this year, nearly double the number from five years before, according to research from cable network FX. TV critics and other overscheduled viewers now refer to this production glut (only partially in jest) as “peak TV,” and that doesn’t even include the backlog of older shows that many people use streaming sites to catch up on.

At Sunday’s Emmy Awards, host Andy Samberg parodied the plight of the buried viewer with a bit about locking himself in a bunker to watch every show available. The fall TV season, which officially began this week, brings the premiere of 44 more shows from broadcasters, not counting freshman series from cable networks.

The new season adds urgency to the TV courtship process, as viewers flirt with unfamiliar shows before diving into a long-term relationship or breaking up with them. Both outcomes involve certain rituals, such as adding or deleting titles from a DVR device.

A scene from ‘The Strain’ Photo: Michael Gibson/FX

Last week, Armand Rosamilia, an author of horror novels in Jacksonville, Fla., wrote “I’m done” on his Facebook page, officially ending his fraught relationship with “The Strain,” a vampire series in its second season on FX. The characters’ pattern of vexing behavior (navigating a city plagued by nocturnal demons after dark) was too infuriating for him—and his wife: “She was sick of me yelling at the television,” Mr. Rosamilia says.

Netflix also tracks statistics on attrition—when viewers bail out on a series for whatever reason—but the company declined to share that research.

The data Netflix did release serve its mantra of personalized viewing. Because of the pressure that Nielsen ratings put on traditional TV networks, “the pilot [first episode] may be the most important 60 minutes in a show’s lifespan,” says Mr. Sarandos, “but that’s not the episode that gets [Netflix viewers] hooked. These shows can go on to be very successful later in their run.”

The episode when viewers commit to at least season 1 was often the same from country to country. Whether in Brazil, Sweden or the U.S., almost all viewers who made it to episode 2 of “The Walking Dead,” in which a character gets handcuffed to a pipe as zombies encroach, stuck around for the rest of the season.

In the Netflix series “Grace and Frankie,” Jane Fonda and Lily Tomlin play reluctant friends who discover that their husbands (Martin Sheen and Sam Waterston) have been in love with each other for years.

Showrunner Marta Kauffman, who cocreated “Friends” in the 1990s, says she wasn’t surprised to learn from Netflix that viewers didn’t embrace the show en masse until episode 4. With the plot riding on its title characters, it took a little time for the writers and producers to grasp the importance of the men’s romantic lives. Ms. Kauffman recalls, “When shooting episode 4, we realized how invested we were in all four characters. The show became more populated.”