Thirty seconds is the length most people picture when they think of a TV advert, and it’s the one the whole pricing system is built around. It isn’t the only option, though, and it isn’t always the right one, because the best length for you depends on how much you need to say, how well viewers already know you and how far your airtime budget has to go.
How the length affects the price
Airtime is sold in fixed lengths, of which 10, 20, 30 and 60 seconds are the standard ones, and it’s priced by length. The price is set for a 30-second advert, and every other length is worked out from that.
- A 60-second advert costs twice as much to air as a 30.
- A 40-second advert, which is one of the in-between lengths you can also buy, costs a third more.
- A 20-second advert costs around 80 to 85 per cent of a 30.
- A 10-second advert costs about half.
You’ll notice the shorter lengths aren’t a straight proportion. A 10-second advert is a third of the length but half the price, and that’s deliberate, because if short adverts were too cheap, the breaks would fill up with dozens of them, which would be worse for viewers and for every advertiser in the break.
What those ratios mean in practice is that length is traded against how often you’re seen. For the same money, a 20-second advert can be shown roughly a fifth more often than a 30, and a 10-second advert twice as often. So choosing a length comes down to whether each showing needs to do a lot of work, or whether you’d be better served by more showings that each do a little.
The length makes much less difference to the cost of making the advert, because a 20-second advert needs the same crew, the same kit and often the same day’s filming as a 30. The saving from going shorter is in the airtime, and it’s seldom a reason to expect a smaller production bill.
What each length is good for
With that trade-off in mind, each of the standard lengths has a job it does well, starting with the shortest. A 10-second advert only has room for one thought, which makes it ideal as a reminder of something people already know, such as a sale date or an event, and it works well alongside a longer advert that has already done the explaining. It’s a tough length for introducing a business nobody has heard of, because by the time viewers have worked out what you do, it’s over.
Twenty seconds is a very useful middle ground, and it’s often overlooked. There’s enough time to make a point and give a reason for it, and the saving on airtime means you can be on screen more often. In 2019, a study of campaigns run by smaller advertisers, commissioned by Thinkbox (the marketing body for commercial TV, so it has an interest), found that the best length for them was generally 20 seconds, though it added that this depends on how complicated the message is.
That last condition matters, because thirty seconds is the standard for good reason. There’s room for a small story, a clear message and a proper ending with your name on it. Research into how viewers’ brains respond to adverts, published by Thinkbox itself, found that adverts shorter than 30 seconds often failed to build a strong connection with the viewer, and that 30 seconds seemed to be the best length for developing a story. If you’re new to TV and want people to understand who you are, this is usually the place to start.
Even a 30 fills up quickly, though, as we found when we made a student recruitment advert for South Tyneside College. The tricky part was that a college has a huge range of courses and only 30 seconds to cover them, and we got round it by combining strong shots with a clever edit.
Sixty seconds and longer gives you room to tell a real story and to make people feel something, and longer adverts tend to be better remembered. At twice the airtime cost, they’re mostly used for a launch or a big moment and then followed up with shorter versions. It’s how the big Christmas adverts are often handled, with the full-length version shown at the launch and shorter ones carrying the rest of the campaign.
The best answer is often more than one
You don’t have to be a national retailer to work that way, and you don’t have to pick a single length. A common approach is to make a 30-second advert and cut a 20 and a 10 from the same footage. You launch with the longer one so that people take in the story, and then switch to the shorter ones to keep reminding them for less money.
There’s some evidence that the order matters. In an experiment that Thinkbox published earlier in 2019, which it describes as small in scale, people who had already seen the long version of an advert remembered the short one far better than people who were shown the short one on its own. The long advert had given them the story, so the short one only had to bring it back to mind. We’ve written separately about how to spread a campaign over the months.
It only works if it’s planned from the beginning, because a script written to run for exactly 30 seconds doesn’t always have a 20 hiding inside it. Take ten seconds out of a story and you may lose the scene that made sense of the ending. A voiceover recorded for the full version can’t be trimmed without it showing, so the shorter script usually has to be written and recorded in its own right. The music has to work at each length as well, which is why our composers can supply a track in 30, 20 and 10-second versions when it’s written for the advert.
If we know you’ll want shorter versions, we’ll write and shoot with them in mind. Each version has to be approved as an advert in its own right, so we’ll put them through Clearcast alongside the main one.
Don’t try to say too much
Whatever length you choose, the commonest mistake is trying to fit in more than it will hold. A voiceover that has to be read at double speed, or an ending where the logo flashes past, undoes all the good work. As a rough guide, a comfortably paced voiceover runs at about two and a half words a second, so 30 seconds is around 75 words at the very most, and fewer is nearly always better, because the pictures and the music need room to do their share. There’s no leeway at the end, either, since an advert has to run to exactly the length that’s been bought, and a script that runs a second or two over has to lose them somewhere.
One way to make room is to ask what could be shown instead of said. When we made an advert for AE Publications with their agency, Forward & Thinking, the story was that their practice books had been tested in real classrooms for more than twenty years, which is a strong story but not an easy one to get across in thirty seconds. So instead of talking about the books, the advert shows children using them, at home and in the classroom, and viewers can see for themselves what a voiceover would have struggled to fit in.
Remember to leave room for the ending as well. Your name needs a few seconds on screen to register, and if your advert needs supers, which is the trade’s name for the small text on screen, they have to stay up long enough to be read, and that time comes out of the same thirty seconds.
How we help you choose
We’ll look at what you need to say, who you’re saying it to and what your airtime budget will stretch to, and recommend the length, or the combination, that gives you the most for your money. The easiest way to judge whether an idea fits its length is to see it drawn out scene by scene, and you can ask us for a free storyboard to see how yours would look. For what goes into a good advert once the length is settled, we’ve also written about what makes a TV ad memorable. And because the length of the break matters as well as the length of the advert, there’s a short read on how long ITV ad breaks are.
Keep reading.
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