Controlling LLM Prose

Tutorial · Lesson 2

Calibrate Length to a Reader

Stop guessing word counts; start from the reader's clock

Who this is for: Anyone who has typed “write ~500 words” and wondered why 500.

What you’ll build: You will convert a reading-time target into a defensible word budget and build a prompt that states it precisely.

A word count means nothing until you know who reads and how hard the ideas push back. This lesson replaces arbitrary counts with a two-step calculation: pick a speed band, then multiply by the minutes you may ask for.

  1. 1

    Diagnose the reader's speed band

    Match the material to a reading-speed band. Casual prose runs ~275 WPM; standard non-fiction ~220; dense technical material ~140. Our audience is busy engineers reading a design note—call it Moderate, 220 WPM.

    Reference: Reading Time & Word-Count Calibration

  2. 2

    Choose a time budget, derive the words

    Decide how many minutes you may ask for. A design-note summary deserves about two minutes. 220 WPM × 2 min ≈ 440 words. That is your budget—arrived at from the reader's experience, not a round number.

    Vague askWrite about 500 words on the caching design.
    Calibrated askTarget a 2-minute read at Moderate complexity: 400–450 words at ~220 WPM.
  3. 3

    State it in the prompt

    Fold the number into an explicit instruction. The interactive calculator on the reference page builds this string for you—adjust the minutes and copy the result.

    Reference: Reading Time & Word-Count Calibration

Recap

Length is arithmetic once you name the reader. Speed band × minutes = words. You now have a repeatable way to justify any length target.