How many songs in a 45-minute set?

Most rock and pop songs land somewhere between three and four and a half minutes. Call it three forty-five. Forty-five minutes divided by three forty-five is twelve songs, near enough.

That is where most bands stop calculating. It is also why sets run long.

Three forty-five is a round number, not a measurement. The measured one is 3:53, across 121 songs that covers and function bands actually play, and the spread around it matters more than the middle does: how long the average song is.

Between songs you retune, somebody says something, a guitar gets swapped, the drummer adjusts a stand. Fifteen seconds is quick. Twenty is normal. Thirty if there is any talking at all.

Twelve songs have eleven gaps between them. At twenty seconds each that is three minutes and forty seconds of your slot, and you did not put it in the plan. That is an entire song.

Plan eleven and you finish on time. Plan thirteen and you get cut off, or you drop something on the fly, and the thing that gets dropped is always the closer.

• Covers run longer than you think. Familiar songs invite an extra chorus, and the crowd is why you added it.
• A support slot is a hard limit. Forty-five means forty-five. Nobody thanks you for forty-eight.
• Talking costs songs. A frontman who introduces every number can spend two songs worth of the set on it.
• A slow closer eats more than its length. If the last song is six minutes, it is really two of your eleven.

And the biggest one, if it applies to you: the slot itself. Forty-five is a support slot, or one set of a longer night. A three-hour pub booking is the same arithmetic with a different trap in it, because the breaks come out of the three hours rather than sitting beside them: how long a 3-hour bar gig setlist should be.

Guessing gets you close. The reason sets still overrun is that nobody knows how long their actual songs are, only roughly how long songs are in general.

Paste your list into Setlists.io and it looks up the real recording of each song, adds the gaps you choose, and tells you what the set runs. If it comes out at forty-seven minutes you find out at the kitchen table, not on stage.

Then the count stops being the question and the sequence starts: how to order a setlist, which is a different problem with its own four ways to get it wrong.