President Trump’s first State of the Union address drew an audience of 45.6 million, about two million fewer than the number who watched his speech to a joint session of Congress a year ago.

The viewership figure, tallied by Nielsen from the broadcast networks and cable channels that aired the 80-minute address on Tuesday night, reflects Mr. Trump’s preferred manner of watching television: the old-fashioned way, on a TV set, in real time. It does not include streaming data.

The television audience was also smaller than the one for President Barack Obama’s first State of the Union address in 2010, which had 48 million viewers.

Mr. Trump’s joint session speech last year drew 48 million viewers, according to Nielsen, about four million fewer than the 52 million who watched Mr. Obama’s joint session speech in 2009. The comparison, though, is complicated by the fact that more people stream these days than they did even five years ago.