As a general rule wider ad sizes tend to outperform their taller counterparts, this is due to their reader-friendly format. Readers absorb information in “thought units”, in several words at a time. The wider sizes allow them to read more text at just a glance without having to skip a line and return to the left margin every few words, as they’d have to with a narrower ad.

If positioned well, wide ad sizes can increase your earnings significantly. The sizes we’ve found to be the most effective are the 336 x 280 large rectangle, the 300 x 250 medium rectangle, the 728 x 90 leaderboard, the 300 x 600 half page and on mobile the 320 x 50 mobile leaderboard. Bear in mind that while these ad sizes will typically perform well, you should always use the size that will complement your pages.

For more information about the different google ad sizes look at the chart below…