Can AI infer how long a video will be from the script automatically?

Yes — AI can infer runtime from a script automatically, and it works two ways: simpler tools estimate duration from word count and average reading speed, while agentic tools read the script's structure and apply the industry rule that one page of screenplay equals roughly one minute of screen time.

Yes — and the accuracy of the inference depends on how the tool reads your script. Basic script-to-video tools calculate duration mechanically: they count words, apply an average narration reading speed, and output an estimate. That works for voiceover-driven explainers, where words on the page map directly to seconds of audio. It breaks down for screenplays, where action lines, pauses, and performance carry time that word count never captures.

Screenplay-format scripts follow the one-page-per-minute rule. Film scripts are formatted so that one page equals approximately one minute of screen time — an industry standard that holds because screenplay formatting normalizes dialogue density and action pacing. An AI tool that understands this doesn't need you to declare a runtime at all: a 5-page script is a ~5-minute film, a 90-page script is a ~90-minute feature. If a tool asks you "how long should this video be?" after you've handed it a properly formatted screenplay, it's signaling that it doesn't understand film structure — the script already answered that question.

Agentic tools infer duration as a byproduct of full script analysis. invideo is an agentic video creation tool, and the invideo agent reads your entire script before generating anything, building a context library of characters, locations, themes, and plot points. Duration falls out of that comprehension automatically: ask it to generate the first five pages and it treats that as the first five minutes of the film — you never decide the runtime independently, the script does. In one documented test where a filmmaker ran a full script through the invideo agent, that upfront script analysis meant characters and scenes "took way less iterations, and were way more story accurate" — duration inference and story accuracy come from the same mechanism.

How to control length in practice. If you need a specific runtime, write to it: trim or expand the script until the page count matches the minutes you want, then hand the whole thing to the invideo agent. If you only need part of the film, request it by page range ("generate pages 1–5") rather than by minutes — page ranges map cleanly to screen time and keep the invideo agent working from script structure instead of an arbitrary duration number. For narration-style scripts rather than screenplays, expect word-count-based estimation instead: roughly 130–150 spoken words per minute is the standard the reading-speed calculators use, so budget your script accordingly.

Watch some of these to see what works for you:

Generally films are written in a way that each page of script is about equivalent to 1 minute of screen time. So, by asking to generate the first five pages, I'm effectively asking to generate the first five minutes of the film. I don't decide the duration independently.

— a filmmaker who tested AI film agents on a full script