Alfred Hitchcock once said “The length of a film should be directly related to the endurance of the human bladder.” Oh, Alfred. What a fun quote! It’s also only somewhat true. If a movie is awful, the bladder will be more liberal in telling you to leave. And I think you’re more likely to hold it if your watching something great. In other words, there is no theory of everything when it comes to hitting the right runtime.

But I want to try anyway. First of all, we’re talking feature length films here. No short films allowed in this conversation. True, you can most definitely tell a coherent, engaging story in just a few minutes, but short films are more like snippets of something larger. Short films are in a different category, one in which the length question is unique to them.

A feature length film is usually marked at 60 minutes. How much story can you get done in that time? As short films prove, quite a lot. Movies that are under 90 minutes generally fly by and don’t mess around with B-plot nonsense. Remember “High Noon?” It isn’t just playing out in real time; it also doesn’t take much time out of your day. “High Noon” is 85 minutes long. That’s an attractive number. We’ll keep that in mind.

What about epic films? I’m referring to those monstrosities that run over 150 minutes. That’s a bit too invasive for me, generally. For every overlong “Ben-Hur,” there’s a “The Godfather Part II.” For every “Gandhi,” there’s a “Pulp Fiction.” Perhaps it depends on the story you’re telling. “Pulp Fiction” could go on for five hours as long as the script is still tight and snappy. “Ben-Hur” might still be a bit of a yawn if it was under two hours. More goes into this than just runtime, but I would say that a three-hour long film is usually unnecessary. Few, including the Coppolas and the Tarantinos, can pull this off. Most of the time, you should be able to tell a story in under two hours. If not, start editing.

I think most people prefer a movie that is around that two-hour mark. In a theater, you want to feel like you got your money’s worth, but also not have to give up an entire day to watch a sewn-together miniseries. (Here’s looking at you, “The Irishman.”) I can’t back this up with any facts and figures, but 132 minutes seems to be a very common film length. I affectionately refer to movies that have this runtime as a “Two-twelve.”

What’s the ideal movie runtime? It depends on a few factors:

• Tell an engaging story in the time and for the audience you’re aiming for.

• Keep the entertainment value high throughout the runtime. Basically, don’t ever let the audience get into a gloomy “is it almost over” mood.

• Satisfy the requirement of a feature-length, 60-minute runtime at least.

As a filmmaker, you have a duty to your audience to make sure your story is balancing depth and engagement. Without these elements, you’ll fail. And while you should know your audience to some degree, the trick is to knock down some preconceived notions that they may have about runtime or otherwise. When you reach that level, I think you can involve the largest possible audience you can.

By the way, 85 minutes is absolutely the ideal movie runtime.