diff --git src/wp-admin/network/settings.php src/wp-admin/network/settings.php
index 1736511..855ffa0 100644
--- src/wp-admin/network/settings.php
+++ src/wp-admin/network/settings.php
@@ -61,7 +61,12 @@ if ( $_POST ) {
 	foreach ( $options as $option_name ) {
 		if ( ! isset($_POST[$option_name]) )
 			continue;
-		$value = wp_unslash( $_POST[$option_name] );
+		if ( $option_name == 'fileupload_maxk' ) {
+			$value = (float)wp_unslash($_POST[$option_name]) * 1024;
+		}
+		else {
+			$value = wp_unslash( $_POST[$option_name] );
+		}
 		update_site_option( $option_name, $value );
 	}
 
@@ -269,7 +274,7 @@ if ( isset( $_GET['updated'] ) ) {
 
 			<tr>
 				<th scope="row"><label for="fileupload_maxk"><?php _e( 'Max upload file size' ) ?></label></th>
-				<td><?php printf( _x( '%s KB', 'File size in kilobytes' ), '<input name="fileupload_maxk" type="number" min="0" style="width: 100px" id="fileupload_maxk" value="' . esc_attr( get_site_option( 'fileupload_maxk', 300 ) ) . '" />' ); ?></td>
+				<td><?php printf( _x( '%s MB', 'File size in MB' ), '<input name="fileupload_maxk" type="number" min="0" step="1" style="width: 100px" id="fileupload_maxk" value="' . round( esc_attr( get_site_option( 'fileupload_maxk', 300 )/1024 ), 2) . '" />' ); ?></td>
 			</tr>
 		</table>