3.11. Design to a 44-Pixel Rhythm

The iPhone looks good, sure, but it feels good, too. The industrial design gurus at Apple carefully designed the iPhone hardware to feel right in your hand, with weight and proportions that are as appealing as the device's glossy sheen. The same should go for your app design, with screens that are not only pretty but are constructed in proportion to the hand, with a sense of balance in each element's visual weight.

Part of that, as you've seen, is a matter of using finger-sized tap targets placed in easy reach. But the size of a fingertip can do more than just determine button sizes: as a unit of measure lifted from the hand itself, fingerspan provides a visual building block for giving your interface design a consistent rhythm in natural proportion to your paw and its pointer. By loosely blocking out your design in a 44-pixel grid, you ensure that interface elements are sized in harmony with one another as well as the fingers that work the device. As you saw earlier, several standard iPhone elements—navigation bars, toolbars, list items, keyboard keys—are sized to 44 pixels, establishing the vertical rhythm of many screens.