In darts, hitting the bulls-eye is harder to do than hitting any other part of the dartboard. This is because the bullseye is the smallest target. This same principle can also apply to touch targets on mobile devices.
Smaller touch targets are harder for users to hit than larger ones. When you’re designing mobile interfaces, it’s best to make your targets big so that they’re easy for users to tap. But exactly how big should you make them to give the best ease of use to the majority of your users? Many mobile developers have wondered this, and most have turned to the user interface guidelines provided by the platform developer for the answer.
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What the Mobile Platform Guidelines Say
Apple’s iPhone Human Interface Guidelines recommends a minimum target size of 44 pixels wide 44 pixels tall. Microsoft’s Windows Phone UI Design and Interaction Guidesuggests a touch target size of 34px with a minimum touch target size of 26px. Nokia’sdeveloper guidelines suggest that the target size should be no smaller than 1cm x 1cm square or 28 x 28 pixels.
While these guidelines give a general measurement for touch targets, they’re not consistent with each other, nor are they consistent with the actual size of the human finger. In fact, their suggested sizes are much smaller than the average finger, which can lead to touch target problems for users on mobile devices.