With over 29 percent of mobile users’ screen time spent looking at smartphones, it’s no wonder that mobile phone sizes are constantly evolving. And, consequently, mobile ad display sizes have changed to accommodate both varying phone and tablet sizes as well as mobile user behavior.

But with all of these new ad display sizes, how do you know which one is the best for mobile advertising campaigns?

Well, I have some bad news and some good news.

Let’s get the bad out of the way, first:

I can’t tell you a universal “best” mobile display ad size for your own unique campaign.

But, I do know a thing or two about the most popular mobile display ad sizes, and I even know which typically perform better than others.

Good news? Sure. However, size isn’t everything.

Even though our super smart Ad Ops guys here at The Mobile Majority have provided me with the top four most popular mobile display ad sizes, don’t just take the information and mindlessly run with it. Instead, be careful to keep in mind who you are targeting and implement additional mobile advertising strategies into your marketing campaigns. To help with this process, consider including a mobile ad platform to help you categorize and target relevant customers with your perfectly-sized ads. (We have a great one called AdSynergy.)

So, what are the most popular mobile display ad sizes?

Below, you will find the top four most popular, including the good and bad news about each to help you decide the best size for your next mobile advertising campaign.

1.) Standard Banner – 320×50

The Mobile Majority Average CTR: 0.45%*

New to mobile advertising, but not sure where to start with mobile ad sizes? This ad size is perfect for mobile ad newbies as its very simple to create.

mobile-ad-display-size-320x50-standard-bannerThe Good News: This mobile ad size is available on all screens, can be executed in large volumes and is super quick to deploy. The standard banner is the most widely accepted size in mobile, as well. In fact, standard banners comprise 60% of available inventory on mobile-optimized sites and apps. 320×50 mobile ads are also rather non-intrusive and don’t tend to disrupt the user experience. Plus, this banner size can be anchored to always be visible on screen, which helps with conversions.

The Bad News: While choosing this size is a good initial strategy as it doesn’t require you to be a mobile ad guru, click through rates (CTRs) just aren’t up to par with those of full-screen interstitials (more on that later). To expand on that, mobile users sometimes succumb to “banner blindness” when this ad type appears on their screens. Yes, this is a real thing where people unconsciously resist clicking on your mobile ads when they appear on the top or bottom of the screen.

2.) Rectangle Banner – 300×250

The Mobile Majority Average CTR: 0.36%*

300x250-mobile-ad-display-sizeAlso known as the medium rectangle banner, the 300×250 is a traditional desktop ad size that’s also rather popular with marketers.

The Good News: Marketers add 300×250 rectangle banners into their mobile ad strategies because the larger size allows for better visualization of your brand’s message – without disrupting your user’s experience. The medium rectangle banner is also very popular on a worldwide scale, so you can take your pick of monetizing any region across the globe.

The Bad News: We tend to see lower CTRs with the 300×250. The reason for this is that this kind of ad is often more of a branding play. That is, its large enough for imagery, but not large enough to be interactive with a unique CTA. We recommend running other ad sizes in addition to this one in order to meet your marketing goals.

3.) Full-Screen Interstitial – 320×480

The Mobile Majority Average CTR: 1.82%*

This larger mobile ad format receives the highest engagement rates, yet is only the third most popular of mobile ad sizes.

mobile-ad-size-320x480The Good News: Want the highest conversion rate possible? Then look to the 320×480 mobile ad. Also known as the full-screen interstitial, this ad size offers premium placement for your ad as it takes up users’ screens entirely. These ads result in high CTRs and better conversions for your brand. Another good thing? The opportunities are endless for amazing, animated and interactive rich media content, which offer visually-compelling ads to your target audience.

The Bad News: While brands are trending toward using more full-screen interstitials in their mobile marketing campaigns, both publishers and developers aren’t serving them up like hot cakes just yet. This is because they don’t want to overstuff users with too many per session for fear that they might explode. So, this means less inventory (320×480 mobile ads account for around 1% of available inventory on mobile-optimized sites and apps). I know, it’s not what you want to hear, but no one wants to blow up out of annoyance — or from overeating, for that matter. So, sometimes pair a larger number of smaller banner ads with full-screen interstitials for ease of consumption — and to increase the effectiveness of your mobile campaign.

4.) Smaller Standard Banner – 300×50

The Mobile Majority Average CTR: 0.72%*

300x50-ad-size-mobileThis mobile ad size is actually the least common, losing both inventory and popularity due to new, larger-sized ad types.

The Good News: Honestly, not too much to say here. In certain contexts, this ad size can work, but that’s largely determined on a case-by-case basis.

The Bad News: This mobile ad size accounts for approximately just 1% of available inventory on mobile-optimized sites and apps.

Did this help? Good! Now, take what you know, but diversify your ad sizes. Meaning, don’t just choose one popular ad size for your mobile advertising campaign. This will help our AdOps professionals shift budgets to whichever ad size happens to be performing better. From there, they can buy more of the better-performing ad sizes which will optimize your advertising campaign for stellar results.

And that’s some seriously good news, isn’t it?

*All performance data listed is for the 2016 year and deviates depending on the nature of the campaigns that were run.