Streaming music services like Spotify have brought big changes to the music industry. But one important part of the business has not kept up: Billboard’s album chart.

Now Billboard and Nielsen SoundScan, the agency that supplies its data, will start adding streams and downloads of tracks to the formula behind the Billboard 200, which, since 1956 has functioned as the music world’s weekly scorecard. It is the biggest change since 1991, when the magazine began using hard sales data from SoundScan, a revolutionary change in a music industry that had long based its charts on highly fudgeable surveys of record stores.

The new chart, covering sales and listening from Monday to Nov. 30, will be revealed on Billboard’s website on Dec. 4 and published in print in its Dec. 13 issue. Silvio Pietroluongo, Billboard’s director of charts, said that by looking at streams as well as sales, the new chart will more accurately reflect how people listen to music these days.

“We were always limited to the initial impulse, when somebody purchased an album,” Mr. Pietroluongo said in an interview. “Now we have the ability to look at that engagement and gauge the popularity of an album over time.”