Study
Do ad sizes matter?
We run responsive units, so AdSense chose the rendered size for every impression. Then we looked at what each size actually earned across a month. The winner was not a size you pick from a dropdown.
The usual version of this question is 300x250 or 336x280, leaderboard or billboard. We had the data to answer it directly: every creative size served across our network for thirty days, with its real viewability, click-through, and RPM. The answer reframes the question.
The highest-earning size was "let the auction choose"
Most of our impressions, 57% of them, were served as Dynamic, the responsive creative AdSense sizes on the fly to fit the slot. It was not only the most common, it earned the most: $2.54 per thousand impressions, more than any fixed size below it. The single best thing we did about size was to stop choosing one. Responsive units let the auction fit the highest-paying creative the space allows, and on our network that beat every size we could have pinned by hand.
Among fixed sizes, the spread is real
When AdSense did serve a fixed size, the gap between them was wide, and it ran along familiar lines.
| Creative size | Share | Viewable | CTR | RPM |
|---|---|---|---|---|
| Dynamic (responsive) | 57% | 53% | 1.3% | $2.54 |
| 970x250 billboard | 1% | 42% | 1.6% | $1.84 |
| 300x250 rectangle | 6% | 41% | 0.9% | $1.50 |
| 300x600 half page | 2% | 45% | 2.3% | $1.41 |
| 336x280 rectangle | 11% | 35% | 0.8% | $1.23 |
| 728x90 leaderboard | 2% | 64% | 0.3% | $0.83 |
| 160x600 skyscraper | 3% | 83% | 0.0% | $0.52 |
| 250x250 square | 6% | 25% | 0.5% | $0.32 |
Served creative size, trailing 30 days, standard display sizes with meaningful volume. Highlighted row is the responsive default. An unlabeled bucket and a mobile interstitial with anomalous clicks are set aside.
The standard rectangles, 300x250, 336x280, 300x600, and the 970x250 billboard, cluster in a respectable band. The odd sizes fall off a cliff: the 250x250 square earned $0.32, a fifth of the Dynamic creative and a quarter of a plain 300x250. If you hand-pick sizes, the only real mistake is picking a strange one.
The most-viewable size earned almost nothing
Look at the 160x600 skyscraper. It was viewable 83% of the time, the best on the board, and it earned $0.52 with not a single click. We say viewability is the lever on this site, and it is, but here is the honest edge of that claim: being seen is necessary, not sufficient. A skinny skyscraper in a sticky rail gets seen and ignored, because demand for that shape is thin. Viewability gets your ad into the auction. It does not make anyone bid.
What it means for you
Run responsive and let the auction size your ads. The size dropdown is not your lever, and trying to outguess it with a fixed size mostly costs you. If you do pin sizes, stay with the standard rectangles and never force a square or a skinny skyscraper. Then put your effort where it moves the number: placement and viewability decide more than any size choice, and the part you cannot control, demand for the format, is one more reason to run the shapes advertisers actually want.
How we measured it
AdSense served-creative size, trailing 30 days, across the sites we run. Our units are responsive, so this is what AdSense chose to serve, not a controlled test that forced each size, and served size is entangled with where each unit sits. We dropped every size under 100 impressions a month as noise. RPM, viewability, and click-through are ratios, not totals. The numbers are real and our own.