docs/html/design/style/metrics-grids.jd

page.title=Metrics and Grids
@jd:body

<p>Devices vary not only in physical size, but also in screen density (<acronym title="Dots per
inch">DPI</acronym>). To simplify the way you design for multiple screens, think of each device as
falling into a particular size bucket and density bucket. The size buckets are <em>handset</em> (smaller than
600<acronym title="Density-independent pixels. One dp is one pixel on a 160 dpi
screen.">dp</acronym>) and <em>tablet</em> (larger than or equal 600dp). The density buckets are <acronym
title="Low density (120 dpi)">LDPI</acronym>, <acronym title="Medium density (160
dpi)">MDPI</acronym>, <acronym title="High density (240 dpi)">HDPI</acronym>, and <acronym title
="Extra-high density (320 dpi)">XHDPI</acronym>. Optimize your application's UI by designing
alternative layouts for some of the different size buckets, and provide alternative bitmap images
for different density buckets.</p>

<div class="layout-content-row">
  <div class="layout-content-col span-8">

    <img src="{@docRoot}design/media/metrics_diagram.png">

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<h4>Space considerations</h4>
<p>Devices vary in the amount of density-independent pixels (dp) they can display.</p>
<p>To see more, visit the
<a href="http://developer.android.com/resources/dashboard/screens.html" target="_blank">
Screen Sizes and Densities Device Dashboard</a>.</p>

  </div>
</div>

<h2 id="48dp-rhythm">48dp Rhythm</h2>

<p>Touchable UI components are generally laid out along 48dp units.</p>

<img src="{@docRoot}design/media/metrics_48.png">

<div class="vspace size-2">&nbsp;</div>

<h4>Why 48dp?</h4>
<p>On average, 48dp translate to a physical size of about 9mm (with some variability). This is
comfortably in the range of recommended target sizes (7-10 mm) for touchscreen objects and users
will be able to reliably and accurately target them with their fingers.</p>
<p>If you design your elements to be at least 48dp high and wide you can guarantee that:</p>
<ul>
<li>your targets will never be smaller than the minimum recommended target size of 7mm regardless of
  what screen they are displayed on.</li>
<li>you strike a good compromise between overall information density on the one hand, and
  targetability of UI elements on the other.</li>
</ul>

<img src="{@docRoot}design/media/metrics_closeup.png">

<div class="vspace size-2">&nbsp;</div>

<h4>Mind the gaps</h4>
<p>Spacing between each UI element is 8dp.</p>

<h2 id="examples">Examples</h2>

<img src="{@docRoot}design/media/metrics_forms.png">