Advert design

Most of us glance at an advert and move on. The company selling the space decides what size it has to be, and writes that down in a specification. The person laying it out starts from there.

Sizes come from whoever sells the space

Each publisher, platform and poster company writes down the sizes it accepts. They change over time. A designer reads the current version before starting.

The Interactive Advertising Bureau (IAB) works with the media and marketing industries in digital advertising. It updated its creative guidelines on 25 February 2025. It notes that many companies still produce traditional fixed-size ad formats. It encourages flexible sizes, which it says "improve delivery across diverse screen sizes and devices".

Display adverts on websites and apps

Google offers two kinds of display advert. A static image ad shows the picture exactly as the advertiser supplied it. A responsive display ad is put together by Google from parts the advertiser uploads, such as headlines, logos, images and descriptions. Google says these ads "automatically adjust their size, appearance and format to fit just about any available ad space".

For a static image ad, Google accepts GIF, JPG and PNG files up to 150 KB (checked on 29 October 2026). Google gives each size width first. The sizes it lists include 300 × 250 (inline rectangle), 728 × 90 (leaderboard), 160 × 600 (wide skyscraper) and 320 × 50 (mobile banner).

Adverts on social media

Meta publishes its own rules in the Meta Ads Guide. It covers image, video, carousel and collection ads. For each format and placement, Meta gives dimensions, file sizes and character limits. A designer checks the guide for the exact spot where the advert will run.

Posters by the road

Poster companies publish a specification for each site or network. JCDecaux lists formats such as the digital 6-sheet and the roadside digital 48-sheet. Its National Drive 48-sheet network runs along main routes in ten cities.

The specification for that network, checked on 29 October 2026, asks for a static JPEG at w612 x h306 pixels, in landscape. Its standard length on screen is 12 seconds, and the network takes static content only.

Television

For a TV advert, the length is what counts. Thinkbox, the marketing body for commercial TV in the UK, says the standard length is 30 seconds. About half of all ads run for 30 seconds. Ads can also run for 10, 20, 40, 50 or 60 seconds or longer. Thinkbox says the length needs to be a multiple of ten seconds to fit the ad break. Its page was last updated on 13 May 2025.

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