Radio Script Timer: How Long Is a 30-Second Script?
If you’ve written a radio script and you’re not sure whether it’ll fit in the time slot you bought, you’re asking the right question. Going long is one of the most common mistakes in radio production, and it’s the kind of mistake that doesn’t show up until the voice talent is in the booth, the clock is running, and the read has to be rushed to fit. By then, fixing it costs studio time you’ve already paid for. The fix is doing the math before recording, not during.
This guide gives you the actual numbers. How many words fit in a 15-, 30-, or 60-second spot. Why the limits are physical rather than stylistic. And how to time your script accurately enough that what you write is what gets recorded.
The short answer: words per second
Conversational English, delivered at a natural pace by a professional voice talent, runs at roughly 2.5 words per second. That’s the working average. Some reads run a little faster (energetic, upbeat reads can push closer to 3 words per second), some run a little slower (warm, contemplative reads might land closer to 2.2). The 2.5 figure is what most experienced producers plan to.
From that single number, the math falls out cleanly. A 15-second spot fits about 38 spoken words. A 30-second spot fits about 75. A 60-second spot fits about 150. Those are the working targets, and writing past them is the single most reliable way to produce a spot that sounds rushed.
Why the limits are hard, not soft
The temptation, when a script comes in over the word count, is to ask the voice talent to read faster. This works less well than people expect. Voice talent can compress a read by maybe 10 to 15 percent before the audio quality starts dropping noticeably. Past that, the read starts to sound hurried. The listener registers the rush even when they can’t articulate what’s wrong, and they associate the rush with low-quality production.
The other thing that happens when a script runs long is that the voice talent has to skip the pauses. Pauses are not dead air. They’re the moments that let key lines land, that let the listener process what was just said, that give music and sound design room to register. A spot crammed wall to wall with words has no breathing room, and breathing room is part of why a well-produced spot feels professional and a homemade spot feels amateur.
The fix is to write to the word count from the start. Knowing that 30 seconds is 75 words forces the script to make choices. The choices are what produce tight, memorable spots. Writing 120 words and asking the talent to compress them is how amateur production gets made.
The numbers in detail
15-second spots: 35 to 40 words
A 15-second spot has time for a hook, one specific idea, and a call to action. That’s it. There’s no room for setup, no room for a story, no room for multiple points. The format works hardest when the spot is anchored on a single line that can carry the whole 15 seconds, with everything else supporting it. Most 15-second scripts fail because they try to do what a 30-second script does in half the time.
30-second spots: 70 to 80 words
The 30-second spot is the workhorse of radio advertising. It’s long enough to set up a small scene or premise, deliver the idea, and close with a clear call to action. It’s short enough that every word has to earn its place. The 70 to 80 word range gives the voice talent enough breathing room to deliver the read at a natural pace with intentional pauses. Push past 80 and the pauses disappear; the spot starts sounding tight.
60-second spots: 140 to 160 words
A 60-second spot is twice the time and almost exactly twice the word count, but it’s not just a longer version of a 30. The longer format allows for actual narrative — a setup, a development, a payoff — which means the writing approach changes. The risk in 60s is the opposite of 15s: not too crowded, but too leisurely. A 60-second spot that wanders loses the listener at 22 seconds and doesn’t get them back.
10-second spots and station tags: 22 to 28 words
Short-form tags and station-bumper spots are rare but worth understanding. At 10 seconds, the spot fits maybe 25 words, and there’s room for almost nothing except brand name, one defining detail, and a call to action. These work as reinforcement around larger campaigns, not as standalone advertising.
How to time a script accurately before recording
Word count gets you in the right neighborhood. Actually timing the script — reading it aloud at performance pace with a stopwatch — gets you to the right answer. The two approaches together are what professionals use.
The fastest way to time a script is to read it aloud yourself, in roughly the tone and pace you want the final spot to use, with a timer running. Read it three times. Take the average. If it’s coming in over the time slot, cut. If it’s coming in under, you have room to slow down for emphasis or add a beat of silence where it’ll land. Most people, the first time they do this, are surprised how much faster they read on the page than they would in performance. That’s why reading aloud matters; silently scanning the script is faster than spoken delivery and produces unreliable estimates.
The most accurate way to time a script without booking studio time is to use a dedicated script timer that calculates duration based on word count and speaking rate. The Killerspots script counter tool is built for exactly this purpose — paste in a script, and the tool returns an estimated read time based on standard spoken-English pace. It’s a free utility, and using it before recording catches length problems while they’re still cheap to fix.
What changes the words-per-second average
The 2.5 words-per-second figure is an average. A few factors can move it in either direction, and knowing them helps you plan more precisely.
Energetic reads run faster. A spot for a car dealership running a weekend sale will move at a different pace than a spot for a funeral home. The energetic read might fit a few extra words in the same time slot, but it’ll also feel different. Picking pace before you write helps you write to the right word count for the right tone.
Technical or unfamiliar terms slow a read down. A medical practice spot that has to include “interventional radiology” or a financial services spot with “fiduciary responsibility” eats time that a simpler vocabulary wouldn’t. Long brand names or long phone numbers do the same. The script needs to budget time for those pieces, which usually means fewer total words overall.
Conversational dialogue between two voices runs slightly slower than a single-voice read, because the two voices have to leave room for each other. A two-voice 30-second spot fits closer to 65 to 70 words than the 75 word target for single-voice.
Music and sound effects don’t change the words per second, but they do change how much space the words have. A spot with a music bed that needs room to develop, or sound effects that need to register clearly, has less time for words than a wall-to-wall voice spot. Budget the time accordingly during scriptwriting, not after.
The other half of timing: pacing within the spot
Word count tells you whether the script will fit. It doesn’t tell you whether the script will work. A spot that runs exactly 30 seconds but uses all of them at the same pace will feel monotonous. A spot that varies pace — slower at the hook, faster through the middle, slowing again at the call to action — will feel dynamic and intentional even though the total word count is the same.
This is part of why scripts get rewritten in the studio. The producer hears the read, identifies where the pace needs to vary, and adjusts either the script or the direction to the voice talent. Writing scripts that already account for pacing — short sentences where you want the read to pop, longer sentences where you want the read to flow — saves time in the studio and produces stronger spots.
What to do once your script times correctly
A script that fits the time slot is the foundation, not the finish. From there, the work is casting the right voice, selecting or composing music that supports the spot, designing the sound, and recording multiple takes to find the version of the read that lands hardest. The script-timing step is upstream of all of that, which is why getting it right saves money and frustration later.
For more on what working radio scripts look like in finished form, the guide to writing a radio ad script covers the structural moves that separate scripts that perform from scripts that fill the time. The script timing rules above are necessary but not sufficient. A script can hit 75 words exactly and still be a forgettable spot if the writing underneath the word count isn’t doing the work.
If you’d rather have the script written by people who do this every week, that’s what the Killerspots
