If you have been working with websites for some time, it shouldn’t come as a surprise that the ad sizes you choose to display on your site can have a dramatic impact on AdSense earnings.
Depending on the layout of your site, performance of different ad sizes can vary greatly. Generally speaking, AdSense has a few ad sizes they recommend that are most effective. They are as follows: 336×280 large rectangle, the 300×250 medium rectangle, the 728×90 leaderboard, the 300×600 half page, and on mobile the 320×100 large mobile banner (not pictured here).
*You can review the complete AdSense guide to ad sizes here.
Another rule of thumb to keep in mind is that vertical ad units usually perform better than horizontal ones. This is simply due to them staying on the screen longer. While the sizes mentioned above should have the biggest impact on your AdSense earnings, you should also consider viewability rates by ad size –