IAB Standard Ad Sizes: The Complete Guide to Banner Dimensions That Actually Perform
The 300x250 medium rectangle is the highest-performing banner size on the internet. It commands 40% higher CPM than the 728x90 leaderboard, maintains 3.2% CTR on average, and achieves 65%+ viewability. But the best size for your site depends on layout, device mix, and traffic tier. This guide covers every IAB standard size, real performance data by position and device, and a framework for choosing which sizes maximize revenue.
What Are IAB Standard Ad Sizes and Why Do They Matter?
IAB standard ad sizes are fixed dimensions that work across ad networks, ad servers, DSPs, and publisher platforms without custom integration. IAB Tech Lab maintains the specification. Standardization lets advertisers reuse creatives across thousands of publishers without resizing. The current baseline is the IAB New Ad Portfolio (2017), which deprecated legacy sizes and introduced the Flexible Ad Format (FlexAd) for responsive environments.
What Are the Standard IAB Banner Sizes?
The IAB New Ad Portfolio defines 14 primary standard sizes across desktop, mobile, and universal categories. The most widely supported account for 90%+ of programmatic display inventory.
IAB Standard Ad Sizes — Relative Scale
[Grid layout showing all major IAB standard ad sizes scaled to relative proportions: 728x90 (leaderboard), 970x250 (billboard), 300x250 (medium rectangle), 300x600 (half-page), 160x600 (wide skyscraper), 320x50 (mobile banner), 320x100 (large mobile banner). Each labeled with dimensions and common name.]
Med Rect
Half Page
Skyscraper
| Size | Common Name | Category | Market Support |
|---|---|---|---|
| 300x250 | Medium Rectangle | Universal | Very High |
| 728x90 | Leaderboard | Desktop | Very High |
| 300x600 | Half Page | Desktop | High |
| 160x600 | Wide Skyscraper | Desktop | Medium |
| 970x250 | Billboard | Desktop | Medium |
| 320x50 | Mobile Banner | Mobile | Very High |
| 320x100 | Large Mobile Banner | Mobile | High |
| 468x60 | Full Banner | Desktop | Low (deprecated) |
| 120x600 | Skyscraper | Desktop | Low (deprecated) |
Avoid deprecated sizes. Programmatic demand for 468x60 and 234x60 is minimal. No major DSP runs campaigns targeting them.
Which Desktop Banner Sizes Perform Best?
The 300x250 medium rectangle and 300x600 half-page are the top desktop performers by CPM and viewability. The 728x90 leaderboard wins on raw impression volume because it sits at the page header, but earns lower CPM than the two rectangle formats.
300x250 (medium rectangle): In-content placement achieves 3.2% average CTR, $2.50 to $4.00 CPM above the fold, and 65 to 72% viewability. Its near-square shape fits naturally in content columns and is the most universally supported size across all programmatic platforms.
300x600 (half-page): The highest-CPM standard banner. Sticky sidebar commands $4.00 to $8.00 CPM, 75 to 90% viewability, and 1.8 to 2.5% CTR. Larger canvas attracts premium brand advertisers.
728x90 (leaderboard): Above-fold header commands $2.00 to $4.00 CPM and 55 to 70% viewability. Below-fold drops to $0.80 to $1.50 CPM. A publisher placing both earns a 3x CPM gap between the two positions on the identical unit.
How Do Mobile Banner Sizes Differ from Desktop?
Mobile requires different thinking on size selection. Users scroll faster on mobile, viewability windows are shorter, and most mobile sessions run on 375 to 428px viewport widths. Forcing a 728x90 leaderboard on mobile (by making it smaller) reduces its market demand significantly.
320x50 (mobile banner): Sticky anchor at the bottom of the mobile viewport achieves 90%+ viewability and $1.00 to $2.50 CPM. Additive revenue that doesn't compete with in-content placements.
320x100 (large mobile banner): 40 to 60% more CPM ($1.50 to $3.50) than 320x50 at comparable viewability. Prioritize it over 320x50 where your mobile layout accommodates it.
300x250 on mobile: The dominant mobile in-content performer. Placed after paragraph 2 or 3, it achieves $1.80 to $3.20 CPM and 55 to 65% viewability. Responsive units in this position outperform fixed 300x250 by 10 to 25% on fill rate.
What Are the Performance Benchmarks by Size?
Performance Heatmap by Ad Size and Placement
[Performance heatmap table with ad sizes as rows and placement/metric as columns. Rows: 300x250, 728x90, 300x600, 320x50, 320x100. Columns: Above-fold CPM, Below-fold CPM, CTR (%), Viewability (%). Cells colored from red (low) to green (high) within each metric column. 300x600 above-fold leads on CPM, 300x250 in-content leads on CTR, 300x600 sticky leads on viewability, 320x50 anchor leads on mobile viewability.]
| Size | Above-Fold CPM | Below-Fold CPM | Avg CTR | Viewability |
|---|---|---|---|---|
| 300x250 in-content | $2.50–4.00 | $1.20–2.00 | 3.2% | 65–72% |
| 728x90 header | $2.00–4.00 | $0.80–1.50 | 1.5–2.5% | 55–70% |
| 300x600 sidebar | $4.00–8.00 | $2.00–3.50 | 1.8–2.5% | 75–90% |
| 320x50 anchor | $1.00–2.50 | N/A (anchor) | 0.5–1.0% | 90%+ |
| 320x100 mobile | $1.50–3.50 | $0.80–1.80 | 1.2–1.8% | 55–65% |
The key insight: size matters less than placement. A 728x90 above-fold outperforms a 300x600 below-fold despite being a smaller unit. Advertisers buying on vCPM pay a premium for confirmed visibility regardless of size. Check these figures against CPM benchmarks for your vertical.
Where Should Each Size Be Placed?
Placement determines 60 to 70% of a banner's revenue performance. The right size in the wrong position underperforms the wrong size in the right position.
Optimal Ad Placement Layout
[Page layout mockup showing a desktop article page. Header zone: 728x90 leaderboard labeled "above-fold, $3.20 CPM." Left sidebar: 160x600 skyscraper labeled "moderate, $1.80 CPM." Right sidebar: 300x600 sticky labeled "premium, $6.00 CPM." In-content after paragraph 3: 300x250 labeled "highest CTR position, $3.50 CPM." Below article: 728x90 labeled "below-fold, $1.10 CPM." Mobile version panel showing 300x250 in-content and 320x50 anchor at bottom.]
300x250: After paragraph 2 or 3 for in-content position. User reading flow naturally pauses here. Don't force it into a narrow sidebar where viewability drops.
300x600: Sticky sidebar is the only position that delivers full potential. Non-sticky sidebar achieves 40 to 50% viewability. Sticky follows the user's scroll for 80 to 90%.
728x90: Header-only. Below-fold leaderboards at $0.80 to $1.50 CPM barely justify the page weight they add. Use as AdSense passback only.
Should You Use Responsive or Fixed Ad Sizes?
Responsive ad units adapt their dimensions to fit the available container. Fixed units have rigid dimensions that must be specified at implementation. Both serve different needs.
Fixed sizes suit premium placements where you're maximizing CPM for a known position (300x600 sticky sidebar, 728x90 header). Fixed sizes attract more DSP creative types because advertisers specifically target those dimensions.
Responsive units suit in-content positions on mixed-device sites. If 50%+ of your traffic is mobile, responsive units produce 10 to 25% more revenue than fixed 300x250 because they match the full range of creative sizes DSPs run. Google's “fluid” AdSense unit and responsive display ads in GAM are the most widely supported implementations.
What About Deprecated and Flexible Sizes?
The 2017 IAB New Ad Portfolio deprecated 18 sizes. Most common survivors in older stacks: 468x60 full banner and 120x600 skyscraper. Both receive minimal programmatic demand. The IAB Flexible Ad Format (FlexAd) allows ads to resize within defined minimum and maximum dimensions (4:1, 2:1, 1:1 aspect ratios). FlexAd has good support in managed network stacks (Mediavine, Raptive) but uneven support across open programmatic exchanges. For rich media advertising, verify which sizes your DSP partners support.
Which Sizes Are Supported Where?
| Platform | Best Supported Sizes | Notes |
|---|---|---|
| Google AdSense | 300x250, 728x90, 320x50, responsive | Auto Ads handles sizing automatically |
| Google Ad Manager | All IAB standard + custom | Manual line item configuration |
| Programmatic open exchange | 300x250, 728x90, 300x600, 320x50 | Top 5 sizes get 90%+ of bid volume |
Programmatic demand concentrates on 4 to 5 sizes. A 970x250 billboard gets a fraction of the bid density of a 300x250. Unusual sizes mean lower fill rates and CPMs.
How Do You Choose the Right Sizes for Your Site?
Start with the universal performers, then layer in format-specific units based on your layout.
Mobile-first sites (70%+ mobile): 300x250 in-content and 320x50 anchor are non-negotiable. Add 320x100 if your layout allows. Skip desktop-only leaderboards.
Desktop-heavy sites (60%+ desktop): 728x90 above-fold header, 300x250 in-content, 300x600 sticky sidebar covers the three highest-CPM positions.
Mixed traffic: Responsive units in-content, fixed 300x600 for desktop sticky, 320x50 anchor for mobile. One worked example: a food blog (75% mobile) running only 728x90 and fixed 300x250 saw mobile CPM at $0.90. After switching in-content to responsive and adding a 320x50 anchor, mobile RPM increased 35%.
Use the CPM calculator to model each size against your traffic volume, and the CTR calculator to compare current and projected yield.
For formats that go beyond standard banners, explore video ad formats for instream and outstream specs, native ads vs display for engagement comparisons, and interstitial ads for full-screen overlay performance. Each format builds on the standard size framework covered in this Display Ad Formats series.
Frequently Asked Questions About IAB Standard Ad Sizes
What are IAB standard ad sizes?
IAB standard ad sizes are fixed banner dimensions defined by IAB Tech Lab that work across all major ad networks, DSPs, and publisher platforms. They enable advertisers to reuse creative assets across thousands of sites without custom resizing, with the current spec based on the 2017 IAB New Ad Portfolio.
What does 300x250 ad size stand for?
300x250 is the “medium rectangle” — 300 pixels wide by 250 pixels tall. It is the most universally supported display ad size, achieving 3.2% average CTR in-content with 65%+ viewability and the highest programmatic bid volume of any standard banner.
How does 728x90 leaderboard perform compared to other sizes?
The 728x90 leaderboard earns $2.00 to $4.00 CPM above the fold and 55 to 70% viewability. It generates high impression volume as a header unit but achieves lower CPM than the 300x250 medium rectangle and significantly lower than the 300x600 half-page.
What is the best mobile banner size?
The 320x50 mobile banner is the standard for sticky anchor placement with 90%+ viewability. For higher CPM, the 320x100 large mobile banner earns 40 to 60% more. For in-content mobile placements, the 300x250 medium rectangle outperforms both on total revenue.
What are the most common ad sizes in 2026?
The five most common ad sizes in 2026 are 300x250 (medium rectangle), 728x90 (leaderboard), 300x600 (half-page), 320x50 (mobile banner), and 320x100 (large mobile banner). These five sizes account for over 90% of all programmatic display bid volume.
Should I use responsive or fixed ad sizes?
Use fixed sizes for premium placements like sticky sidebars and headers where specific DSP targeting maximizes CPM. Use responsive units for in-content positions on mixed-device sites, where they produce 10 to 25% more revenue than fixed 300x250 by matching a wider range of creative sizes.