Index: src/wp-admin/css/common.css
===================================================================
--- src/wp-admin/css/common.css	(revision 41321)
+++ src/wp-admin/css/common.css	(working copy)
@@ -3737,6 +3737,15 @@
 	}
 }
 
+@media screen and (max-width: 375px) {
+	.mobile-clear-both {
+		clear: both;
+		display: block;
+		padding-top: 5px;
+		padding-bottom: 5px;
+	}
+}
+
 @media screen and (max-width: 320px) {
 	/* Prevent default center alignment and larger font for the Right Now widget when
 	   the network dashboard is viewed on a small mobile device. */
Index: src/wp-admin/css/forms.css
===================================================================
--- src/wp-admin/css/forms.css	(revision 41321)
+++ src/wp-admin/css/forms.css	(working copy)
@@ -1220,7 +1220,7 @@
 	input[type="number"].small-text,
 	.form-table input[type="text"].small-text {
 		width: auto;
-		max-width: 55px;
+		max-width: 70px;
 		display: inline;
 		padding: 3px 6px;
 		margin: 0 3px;
Index: src/wp-admin/options-media.php
===================================================================
--- src/wp-admin/options-media.php	(revision 41321)
+++ src/wp-admin/options-media.php	(working copy)
@@ -52,10 +52,14 @@
 <tr>
 <th scope="row"><?php _e('Thumbnail size') ?></th>
 <td>
+<span class="mobile-clear-both">
 <label for="thumbnail_size_w"><?php _e('Width'); ?></label>
 <input name="thumbnail_size_w" type="number" step="1" min="0" id="thumbnail_size_w" value="<?php form_option('thumbnail_size_w'); ?>" class="small-text" />
+</span>
+<span class="mobile-clear-both">
 <label for="thumbnail_size_h"><?php _e('Height'); ?></label>
 <input name="thumbnail_size_h" type="number" step="1" min="0" id="thumbnail_size_h" value="<?php form_option('thumbnail_size_h'); ?>" class="small-text" /><br />
+</span>
 <input name="thumbnail_crop" type="checkbox" id="thumbnail_crop" value="1" <?php checked('1', get_option('thumbnail_crop')); ?>/>
 <label for="thumbnail_crop"><?php _e('Crop thumbnail to exact dimensions (normally thumbnails are proportional)'); ?></label>
 </td>
@@ -64,10 +68,14 @@
 <tr>
 <th scope="row"><?php _e('Medium size') ?></th>
 <td><fieldset><legend class="screen-reader-text"><span><?php _e('Medium size'); ?></span></legend>
+<span class="mobile-clear-both">
 <label for="medium_size_w"><?php _e('Max Width'); ?></label>
 <input name="medium_size_w" type="number" step="1" min="0" id="medium_size_w" value="<?php form_option('medium_size_w'); ?>" class="small-text" />
+</span>
+<span class="mobile-clear-both">
 <label for="medium_size_h"><?php _e('Max Height'); ?></label>
 <input name="medium_size_h" type="number" step="1" min="0" id="medium_size_h" value="<?php form_option('medium_size_h'); ?>" class="small-text" />
+</span>
 </fieldset></td>
 </tr>
 
@@ -74,10 +82,14 @@
 <tr>
 <th scope="row"><?php _e('Large size') ?></th>
 <td><fieldset><legend class="screen-reader-text"><span><?php _e('Large size'); ?></span></legend>
+<span class="mobile-clear-both">
 <label for="large_size_w"><?php _e('Max Width'); ?></label>
 <input name="large_size_w" type="number" step="1" min="0" id="large_size_w" value="<?php form_option('large_size_w'); ?>" class="small-text" />
+</span>
+<span class="mobile-clear-both">
 <label for="large_size_h"><?php _e('Max Height'); ?></label>
 <input name="large_size_h" type="number" step="1" min="0" id="large_size_h" value="<?php form_option('large_size_h'); ?>" class="small-text" />
+</span>
 </fieldset></td>
 </tr>