Sentence-length variety is what makes prose feel alive. Strunk and White, Stephen King, Gary Provost: every prose teacher hammers it. This tool measures your variety with a coefficient-of-variation score (0–100), plots a length histogram, and flags any run of three or more same-length sentences in a row.
Why this matters
Gary Provost wrote the most famous demonstration of this principle:
This sentence has five words. Here are five more words. Five-word sentences are fine. But several together become monotonous. Listen to what is happening. The writing is getting boring. The sound of it drones. It's like a stuck record. The ear demands some variety.
Now listen. I vary the sentence length, and I create music. Music. The writing sings. It has a pleasant rhythm, a lilt, a harmony. I use short sentences. And I use sentences of medium length. And sometimes, when I am certain the reader is rested, I will engage him with a sentence of considerable length, a sentence that burns with energy and builds with all the impetus of a crescendo, the roll of the drums, the crash of the cymbals, sounds that say listen to this, it is important.
That's the entire principle. The first paragraph scores low on variety. The second scores high. Read them aloud and you'll hear the difference instantly.
What the score tells you
- 0–30 (monotone). Your sentence lengths cluster tightly. Reads as flat unless deliberate (some literary minimalism, dialogue-heavy scenes).
- 30–60 (healthy variety). Most readable prose lives here. Mix of short, medium, occasional long.
- 60+ (highly varied). Deliberate rhythmic range. Common in literary fiction, lyrical essays, well-crafted long-form journalism.
Genre matters. Legal and technical writing routinely score under 30 and that's fine. The goal is informational, not musical. Thrillers often score in the 40s with strategic short bursts during action. Literary fiction can score 70+ with long lyrical passages broken by abrupt fragments.
How to use the highlighted runs
- Read the run aloud. If it sounds deliberate (a string of short sentences building tension), leave it.
- If it sounds flat, vary one or two. Combine two short sentences with a connector ("She walked to the door. She opened it." → "She walked to the door and opened it."). Or split a sentence in half. Even a small change breaks the rhythmic monotony.
- Don't fix everything. If your variety score is 28 across an action scene, the short sentences might be exactly right. Score is a flag, not a verdict.
What this tool can't do
It counts words per sentence. It doesn't read for semantic variety, whether your sentences vary in syntax, opening word, clause structure. A passage of all "She [verbed] [object]" can score high on length variety while still feeling monotone for syntactic reasons. For that, read aloud.
It also can't tell intentional from accidental monotony. That's your judgment. The tool surfaces patterns; you decide which to keep.