1page.title=Metrics and Grids 2page.metaDescription=Optimize your app's UI by designing layouts based on density-independent grids. 3page.tags="layout","screens" 4meta.tags="multiple screens, layout, tablets" 5page.image=/design/media/metrics_closeup.png 6@jd:body 7 8<p>Devices vary not only in physical size, but also in screen density (<acronym title="Dots per 9inch">DPI</acronym>). To simplify the way you design for multiple screens, think of each device as 10falling into a particular size bucket and density bucket:</p> 11<ul> 12 <li>The size buckets are <em>handset</em> (smaller than 13600<acronym title="Density-independent pixels: One dp is one pixel on a 160 dpi (mdpi) 14screen.">dp</acronym>) and <em>tablet</em> (larger than or equal 600dp).</li> 15 <li>The density buckets are <acronym 16title="Low density (120 dpi)">LDPI</acronym>, <acronym title="Medium density (160 17dpi)">MDPI</acronym>, <acronym title="High density (240 dpi)">HDPI</acronym>, <acronym title 18="Extra-high density (320 dpi)">XHDPI</acronym>, <acronym title 19="Extra-extra!-high density (480 dpi)">XXHDPI</acronym>, and <acronym title 20="Extra-extra-extra!-high density (640 dpi)">XXXHDPI</acronym>.</li> 21</ul> 22 23<p>Optimize your application's UI by designing 24alternative layouts for some of the different size buckets, and provide alternative bitmap images 25for different density buckets.</p> 26 27<p>Because it's important that you design and implement your layouts for multiple densities, 28the guidelines below and throught the documentation 29refer to layout dimensions with <acronym title="Density-independent pixels: One dp is one pixel 30on a 160 dpi (mdpi) screen.">dp</acronym> measurements instead of pixels.</p> 31 32 33<div class="layout-content-row"> 34 <div class="layout-content-col span-8"> 35 36 <img src="{@docRoot}design/media/metrics_diagram.png"> 37 38 </div> 39 <div class="layout-content-col span-5"> 40 41<h4>Space considerations</h4> 42<p>Devices vary in the amount of density-independent pixels (dp) they can display.</p> 43<p>To see more, visit the 44<a href="http://developer.android.com/resources/dashboard/screens.html" target="_blank"> 45Screen Sizes and Densities Device Dashboard</a>.</p> 46 47 </div> 48</div> 49 50 51<h2 id="48dp-rhythm">48dp Rhythm</h2> 52 53<p>Touchable UI components are generally laid out along 48dp units.</p> 54 55<img src="{@docRoot}design/media/metrics_48.png"> 56 57<div class="vspace size-2"> </div> 58 59<h4>Why 48dp?</h4> 60<p>On average, 48dp translate to a physical size of about 9mm (with some variability). This is 61comfortably in the range of recommended target sizes (7-10 mm) for touchscreen objects and users 62will be able to reliably and accurately target them with their fingers.</p> 63<p>If you design your elements to be at least 48dp high and wide you can guarantee that:</p> 64<ul> 65<li>your targets will never be smaller than the minimum recommended target size of 7mm regardless of 66 what screen they are displayed on.</li> 67<li>you strike a good compromise between overall information density on the one hand, and 68 targetability of UI elements on the other.</li> 69</ul> 70 71<img src="{@docRoot}design/media/metrics_closeup.png"> 72 73<div class="vspace size-2"> </div> 74 75<h4>Mind the gaps</h4> 76<p>Spacing between each UI element is 8dp.</p> 77 78<h2 id="examples">Examples</h2> 79 80<img src="{@docRoot}design/media/metrics_forms.png"> 81
