Nothing on the sports calendar is as vast and complicated for a TV network to cover as a summer Olympics, and therefore nothing is as complicated to analyze for those who closely follow television ratings and viewership.

It is too soon to tell exactly how NBC’s coverage of the Games in Rio will stack up historically, but after a sluggish start things have begun to improve behind a strong showing from American gymnasts and swimmers.

Through Tuesday prime time, NBC-only coverage was averaging 15.6 percent of homes and 28.6 million viewers — spectacular, NFL-caliber numbers compared to most sports events but down from 2012 in London.

That gap has been closing, though. Most recently, NBC averaged 33.4 million viewers Tuesday on a night when swimmers Michael Phelps and Katie Ledecky won gold, as did the U.S. women’s gymnastics team.

NBC continues to crush all other broadcast network programming, as is customary for the Olympics during TV’s August dog days.

Complicating comparisons to prior Olympics — and keeping ratings analysts busy — is the ever-growing coverage on NBC’s cable television outlets as well as live streaming of all events.

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NBC said that through Tuesday, its Olympics coverage had generated 883 million minutes of live streaming, more than the 818 million for the entire 2012 Olympics.

On Tuesday NBC issued its first Total Audience Delivery figures for live prime time coverage, saying that Monday night’s drew an 18.1 rating and 31.5 million viewers when all television and digital platforms were included.

On Wednesday it said that the total audience figures for Tuesday night were a 20.5 rating and 36.1 million viewers.

In an interview with USA Today, NBC Olympics’ executive producer Jim Bell called traditional Nielsen ratings a “measurement tool from the 1970s . . . The architecture of this operation is such that we’re building it for the future. And not just how people have been consuming the Olympics for the last 30 years, but how we expect they will be consuming it for the next 30 years.”

Salt Lake City was the highest-rated major market for Tuesday night’s coverage, as it has been most days, at an average of 30.6 percent of homes, followed by Denver’s 28.7.