Best Ad Sizes for Mobile: Publisher's Revenue Guide 2026

Mobile traffic now accounts for over 60% of total web traffic worldwide, and for many content verticals that number exceeds 75%. Yet a surprising number of publishers still run their mobile ad stack using desktop-era thinking: wrong sizes, poor placement, and zero consideration for how a 6-inch screen differs from a 24-inch monitor. The result is money left on the table at every impression.

Choosing the right mobile ad sizes is not a minor optimization. The difference between a poorly sized mobile ad unit and an optimally configured one can be 2-3x in eCPM. This guide ranks every major mobile ad size by revenue performance, explains when to use each one, and covers the responsive and sticky formats that maximize yield without destroying user experience.

Why Mobile Ad Sizes Matter More Than You Think

On desktop, ad size selection is relatively forgiving. A 728x90 leaderboard and a couple of 300x250 medium rectangles will get you within range of optimal performance. The screen is large enough that most standard IAB sizes render well and attract competitive demand.

Mobile is different. Screen width is constrained to 320-428 CSS pixels on most devices, which immediately eliminates wide desktop formats. Viewport height is limited and shared between content, browser chrome, and any sticky UI elements. Every pixel of ad space competes directly with content for the user's attention and patience.

The stakes are higher too. Mobile users have shorter session durations (averaging 2-3 minutes versus 5-7 minutes on desktop), which means each ad impression carries more weight. If your mobile ad configuration shows a low-eCPM 320x50 banner where a 300x250 could fit, you are losing revenue on every single pageview from the majority of your audience.

Beyond raw eCPM, ad size affects three critical metrics:

• Fill rate: Common sizes like 300x250 have near-100% fill because every advertiser has creatives in that format. Unusual sizes may see 60-80% fill, meaning you serve blanks on a significant percentage of impressions.
• Viewability: Smaller ads placed in-content achieve higher viewability than large ads placed below the fold that users never scroll to. Viewability directly impacts how much advertisers bid.
• Core Web Vitals: Ads that cause layout shifts (CLS) or slow rendering (LCP) hurt your search rankings. Properly sized, reserved-space ad containers prevent both problems.

Top Mobile Ad Sizes Ranked by Revenue

The following ranking is based on aggregate eCPM data across thousands of publisher sites in mixed verticals and Tier 1 geographies (US, UK, CA, AU, DE). Your actual numbers will vary by niche, audience geography, and implementation quality, but the relative ranking is consistent.

1. 300x250 (Medium Rectangle) — Highest eCPM

The 300x250 is the single most important ad size for mobile publishers. It consistently delivers the highest eCPMs of any standard display unit, typically ranging from $2.00-$8.00 in US traffic depending on vertical. Finance, insurance, and health verticals regularly see $6.00-$12.00 eCPMs on well-placed 300x250 units.

Why it earns the most: The 300x250 is a universal size. It is the most widely used ad format across both desktop and mobile, which means virtually every advertiser has creatives ready for it. This creates maximum demand competition in the auction, pushing eCPMs up. It also renders beautifully in mobile content flows, taking up enough screen real estate to be impactful for the advertiser without overwhelming the reader.

Best placement: Between content paragraphs, ideally after the second or third paragraph where the user is engaged but has not yet decided to bounce. A second 300x250 can be placed deeper in the content (after the 5th-7th paragraph) for long-form articles. Avoid placing it directly at the top of the page above content, as this triggers layout shift issues and feels aggressive.

Typical eCPM range: $2.00-$8.00 (general content), $6.00-$12.00 (high-value verticals)

2. 320x480 (Mobile Interstitial) — Highest Revenue Per Impression

Mobile interstitials are full-screen (or near full-screen) ad units that appear between page navigations or at natural content break points. The 320x480 size is the standard mobile interstitial format, though most implementations now use responsive interstitials that scale to fill the device screen.

Why it earns so much: Interstitials command attention. The user must engage with the ad (view it and close it) before continuing to content. This guarantees near-100% viewability and extended time-in-view, both of which advertisers pay premium rates for. Brand advertisers use interstitials for high-impact campaigns where recall matters.

Typical eCPM range: $8.00-$25.00+ in Tier 1 geos. Some publishers in finance and automotive verticals report interstitial eCPMs exceeding $30.00.

The catch: Google strictly regulates interstitials. They must not appear on initial page load (only between page navigations), must have a visible close button, and should not fire more than once per 60 seconds. Overusing interstitials will hurt user retention and may trigger Chrome's built-in ad filtering. Use them strategically: once per session or once per major page navigation is the sweet spot.

3. 300x600 (Half Page) — Premium Inventory

The 300x600 half-page ad takes up significant screen real estate on mobile, making it a high-impact format that attracts premium brand advertisers. On a typical mobile viewport, a 300x600 fills roughly 60-70% of the visible screen when scrolled into view.

Why it works: The large canvas allows for rich media creatives, video ads, and interactive formats that smaller units cannot support. Advertisers running brand awareness campaigns specifically seek out 300x600 inventory because it delivers impact comparable to a magazine full-page ad.

Typical eCPM range: $3.00-$10.00. The eCPM is typically 40-60% higher than a 300x250 in the same position.

Best placement: Mid-content in long-form articles (1500+ words). The content must be long enough that the ad does not dominate the page. On shorter articles, this size feels overwhelming and will increase bounce rates. Also works well as a sidebar unit on tablet viewports.

4. 336x280 (Large Rectangle) — Google Recommended

The 336x280 is Google's recommended upgrade from the 300x250. It provides 20% more ad canvas, which accommodates more creative formats and gives advertisers slightly more room for their message.

Revenue comparison: eCPMs for 336x280 are typically 5-15% higher than 300x250 in the same placement. The improvement comes from the larger canvas attracting some premium creatives that require the extra space. However, advertiser demand (number of bidders) is slightly lower than 300x250 because not all advertisers have 336x280 creatives ready.

Typical eCPM range: $2.20-$8.50. Slightly higher ceiling than 300x250, but the floor is similar.

Best practice: Configure your ad units to accept both 300x250 and 336x280 (multi-size request). This lets the ad server pick whichever size wins the auction, giving you the demand pool of both sizes combined. The container should be sized for 336x280 to accommodate either.

5. 320x100 (Large Mobile Banner) — Strong Sticky Option

The 320x100 large mobile banner is the higher-revenue alternative to the standard 320x50 mobile banner. It takes up twice the vertical space, which allows for more creative content and more impactful ad rendering.

Revenue comparison: The 320x100 delivers approximately 30% higher eCPMs than the 320x50, averaging $1.00-$3.00 in US traffic versus $0.60-$2.00 for the smaller format. The additional height means advertisers can include a call-to-action button, product image, and headline rather than cramming everything into a single narrow strip.

Typical eCPM range: $1.00-$3.00 (inline), $1.50-$4.00 (sticky)

Best use case: Sticky footer bars on mobile where you want higher revenue and your content can tolerate the slightly larger footprint. The 320x100 occupies roughly 15% of a standard mobile viewport, which is the maximum recommended by Google's Better Ads Standards. If your analytics show low bounce rates and long session durations, the 320x100 sticky is worth testing against 320x50.

6. 320x50 (Mobile Banner) — Most Common, Lowest eCPM

The 320x50 mobile banner is the most deployed mobile ad size in the world. It is the default mobile ad format, the standard sticky footer size, and the format most publishers start with. Its ubiquity is both its strength and its weakness.

Why the eCPM is low: The 320x50 is small. Advertisers have limited creative space, which reduces the impact of their message and their willingness to bid high. Supply is enormous (nearly every mobile site runs at least one 320x50), which means advertisers can be selective. The result is consistent but modest eCPMs.

Typical eCPM range: $0.60-$2.00 (inline), $1.00-$3.00 (sticky with refresh)

When to use it: The 320x50 is the right choice for sticky footer bars on sites where user experience is the top priority, for supplementary ad slots where you want incremental revenue without visual disruption, and for high-traffic sites where the low eCPM is offset by massive volume. It is also the safest default for sticky implementations because it takes up minimal viewport space (roughly 7% on a standard mobile screen).

Responsive Ad Sizes and Fluid Units

Fixed ad sizes work well when you know the exact device and context, but the reality of mobile is fragmentation. Screen widths range from 320px on older phones to 428px on newer large-format devices like the iPhone 15 Pro Max. Tablet viewports add another layer of complexity.

Responsive (fluid) ad units solve this by letting the ad server determine the optimal creative size based on the container dimensions. In Google Ad Manager, you configure this by adding "fluid" as a size in your ad unit, or by using multi-size ad requests that list multiple acceptable sizes.

How Fluid Units Work

A fluid ad unit has a container that is set to 100% width with a flexible height. When the ad server receives the request, it knows the available width and selects a creative that fits. The container then adjusts its height to match the delivered creative. This means a fluid unit might serve a 300x250, a 320x100, or a native ad with custom dimensions, depending on what wins the auction.

Revenue impact: Fluid units typically earn 10-25% more than fixed-size units in the same position. The broader pool of eligible creatives increases auction competition. A fixed 300x250 slot only competes among 300x250 creatives, but a fluid slot in the same position competes among 300x250, 336x280, 320x100, native formats, and any custom-sized creative that fits the available width.

Multi-Size Requests

If you prefer more control than a fully fluid unit, multi-size requests let you specify exactly which sizes are acceptable. For a mobile in-content placement, a strong multi-size configuration is: 300x250, 336x280, 320x100, 300x50. The ad server runs an auction across all four sizes and delivers the highest-paying winner.

The key to multi-size requests is reserving container space for the largest possible size. If your multi-size unit can serve a 336x280 or a 320x50, reserve 336x280 worth of space in the layout. When a smaller creative wins, center it in the reserved space. This prevents Cumulative Layout Shift (CLS) from the container resizing after ad load.

Native Ad Units

Native ads are the ultimate responsive format. They match the look and feel of your content, using your site's fonts, colors, and layout patterns. On mobile, native ads blend into the content feed and achieve click-through rates 3-5x higher than standard display banners.

From a size perspective, native ads are inherently fluid. The ad server delivers structured content (headline, image, description, CTA) that your site renders in a template matching your design. There is no fixed pixel size; the ad adapts to whatever container you provide.

Revenue impact: Native ads command eCPMs comparable to 300x250 display ($2.00-$8.00) with better user engagement metrics. The trade-off is lower fill rates in programmatic; not all demand sources support native formats. Use native alongside display in a multi-format strategy rather than relying on native alone.

Mobile Sticky Ad Sizes

Sticky ads on mobile are one of the most reliable revenue generators available. A sticky footer bar runs continuously throughout the user's session, delivering 90%+ viewability and enabling ad refresh that multiplies impressions from a single slot.

320x50 Sticky Footer

The standard mobile sticky footer. It occupies approximately 50 pixels at the bottom of the viewport, leaving 90%+ of the screen for content. This is the format recommended by Google for mobile anchor ads and the one that carries the lowest UX risk.

Revenue profile: With 45-second viewability-gated refresh, a 320x50 sticky footer typically generates $1.50-$4.00 RPM (revenue per thousand pageviews) from initial impressions plus 2-3 refreshes per average session. For a site doing 500,000 monthly mobile pageviews, that is $750-$2,000 per month from a single ad slot.

320x100 Sticky Footer

The large mobile banner sticky format. Double the height of the 320x50, it delivers 30% higher eCPMs but takes up more screen real estate. At 100 pixels tall, it sits right at the 15% viewport threshold that Google considers the maximum for acceptable sticky ads.

When to choose 320x100 over 320x50: If your site has high engagement metrics (average session duration over 2 minutes, pages per session above 2.5), your users tolerate the larger footprint and the higher eCPM is worth it. If your bounce rate is above 60% or session duration is under 90 seconds, stick with 320x50 to avoid pushing marginal users away.

Sticky Implementation Requirements

• Close button: Mandatory. At least 44x44px touch target. Positioned at the top corner of the container. When closed, the ad should stay closed for the page session.
• Delayed appearance: Do not show the sticky bar on initial page load. Wait until the user has scrolled at least 100px, indicating engagement.
• Safe area insets: Use CSS env(safe-area-inset-bottom) to position the bar above the home indicator and gesture zones on modern phones.
• Content padding: Add bottom padding to your page body equal to the sticky bar height plus 10px buffer, so the last line of content is never hidden behind the ad.
• Single sticky rule: Never show more than one sticky ad simultaneously. Running a sticky header and sticky footer together violates the 30% screen coverage limit and feels oppressive to users.

Mobile Interstitial Best Practices

Interstitials are the highest-eCPM format available on mobile, but they are also the most regulated. Get the implementation wrong and Google will flag your site, Chrome may filter your ads, and users will leave.

Timing Rules

Google's interstitial policy is specific about when interstitials can appear:

• Allowed: Between page navigations (user clicks a link, interstitial appears before the next page loads). After a user-initiated action (clicking a "continue" button, submitting a form). Between levels or sections in app-like experiences.
• Not allowed: On initial page load from search results (Google penalizes this in mobile search rankings). While the user is in the middle of reading content. On page exit (exit-intent interstitials are permitted by some networks but Google does not recommend them for AdSense/GAM).

Frequency Capping

Show interstitials no more than once per 60 seconds and no more than 3 times per user session. Publishers who test aggressive interstitial frequency consistently find that revenue increases for 1-2 weeks and then drops as user retention degrades. The sustainable approach is less frequent, higher-impact interstitial placements.

Close Button and Countdown

The close button must appear within 5 seconds of the interstitial loading, ideally immediately. A countdown timer (showing "Skip in 3...2...1") is acceptable for video interstitials but should not exceed 5 seconds for display. The close button must be at least 48x48px and positioned in the top-right corner where users expect it.

Responsive Interstitials

Modern mobile interstitials should be responsive rather than fixed at 320x480. Configure your interstitial ad unit to fill the device screen minus safe area insets. Google Ad Manager's built-in interstitial format handles this automatically when you select the "interstitial" ad type. This ensures the ad looks correct on devices ranging from small Android phones to large iPads.

Common Mobile Ad Size Mistakes

These are the mistakes we see most frequently when auditing publisher mobile ad setups. Each one directly costs revenue.

1. Using Only 320x50 Banners

Many publishers default to 320x50 for every mobile ad slot. This is the lowest-eCPM standard mobile format. Replace in-content 320x50 slots with 300x250 units and you will see an immediate 2-3x eCPM increase. Reserve the 320x50 for sticky footer bars where its small footprint is a feature, not a limitation.

2. Too Many Ads Above the Fold

Cramming a 300x250 and a 320x100 above the fold on mobile means the user's first screen is more than 50% advertising. This violates Google's Better Ads Standards, hurts Core Web Vitals (CLS from multiple ads loading simultaneously), and repels users. Place your first ad unit after the opening paragraph or section heading, not before it.

3. No Size Reservation (CLS Problems)

When an ad loads into a container without reserved dimensions, the page content jumps. On mobile, this jump is highly visible and frustrating. It also fails Google's CLS threshold, damaging your search rankings. Always set explicit min-height on your ad containers matching the expected ad size. For a 300x250 slot: min-height: 250px. For multi-size slots, reserve space for the largest possible size.

4. Using Desktop Sizes on Mobile

A 728x90 leaderboard does not work on a 375px-wide mobile screen. It either overflows horizontally (creating a horizontal scroll bar) or gets scaled down to the point of illegibility. Never request desktop-only sizes in your mobile ad calls. Use responsive detection to serve the correct size set for each device type.

5. Ignoring Viewport Differences

Not all mobile screens are equal. A 320x100 sticky bar takes up 15% of the viewport on a standard phone but over 20% on a small-screen device. Test your ad layout on multiple device sizes using Chrome DevTools device emulation. What looks fine on an iPhone 15 Pro Max might be overwhelming on an iPhone SE.

6. Running Sticky and Interstitial Simultaneously

When an interstitial is displayed, the sticky footer bar should be hidden. Running both at once means the user sees a full-screen ad with another ad peeking out at the bottom, which looks broken and increases accidental clicks (which hurt your ad account standing). Coordinate your sticky and interstitial implementations to avoid overlap.

Frequently Asked Questions

What is the best ad size for mobile websites?

The 300x250 medium rectangle is the best-performing mobile ad size by eCPM, generating 2-3x more revenue per impression than standard mobile banners. It works well placed between content paragraphs and attracts the highest advertiser demand because it is also a standard desktop size, meaning it pulls from the largest possible pool of creatives. For sticky placements, the 320x50 mobile banner is the standard choice due to its small viewport footprint.

How many ads should I show on a mobile page?

Google recommends that ad content should not exceed 30% of the visible page area on mobile at any scroll depth. For most publishers, this means 3-5 ad units on a standard article page: one 300x250 near the top of content, one or two 300x250 units spaced within the body, one sticky footer bar (320x50 or 320x100), and optionally one interstitial on page navigation. More than this typically causes diminishing returns as ad density reduces CPMs across all units.

Are mobile interstitial ads worth using?

Yes, mobile interstitials are among the highest-revenue ad formats available, with eCPMs of $8-$25+ in Tier 1 geos. However, they must comply with Google's guidelines: interstitials should appear between page navigations (not on initial page load), must have a clearly visible close button, and should not appear more than once every 60 seconds. Non-compliant interstitials will trigger Better Ads Standards violations and may result in Chrome filtering your ads entirely.

Should I use responsive ad units or fixed-size ads on mobile?

Use responsive ad units for in-content placements and fixed sizes for sticky placements. Responsive units allow the ad server to select the highest-paying creative that fits the available space, increasing competition and eCPM by 10-25%. For sticky footer bars, fixed sizes (320x50 or 320x100) are better because the container height must be predictable to avoid layout shifts and maintain consistent UX.

What mobile ad sizes does Google Ad Manager support?

Google Ad Manager supports all standard IAB mobile ad sizes including 320x50 (mobile banner), 320x100 (large mobile banner), 300x250 (medium rectangle), 336x280 (large rectangle), 320x480 (mobile interstitial), 300x600 (half page), and fluid/responsive sizes. You can also define custom sizes. For maximum fill rate, configure your ad units with multiple sizes (multi-size requests) so GAM can select from a broader pool of available demand.