diff --git a/config.inc.php b/config.inc.php
index d0a3aaf..afdab6a 100755
--- a/config.inc.php
+++ b/config.inc.php
@@ -14,7 +14,7 @@ define("CUSTOM_TEXT", "This LibreQR instance is hosted by <a href='https://foo.e
 
 // Default values
 define("DEFAULT_REDUNDANCY", "high");
-define("DEFAULT_MARGIN", NULL);
-define("DEFAULT_SIZE", NULL);
+define("DEFAULT_MARGIN", 20);
+define("DEFAULT_SIZE", 300);
 define("DEFAULT_BGCOLOR", "FFFFFF");
 define("DEFAULT_MAINCOLOR", "000000");
diff --git a/index.php b/index.php
index 4d11325..a33bed9 100755
--- a/index.php
+++ b/index.php
@@ -171,13 +171,7 @@ foreach($themeDimensionsIcons as $dimFav) // Set all icons dimensions
 							<?= $loc['help_margin'] ?>
 						</p>
 					</details>
-					<input type="number" list="margins" id="margin" placeholder="<?= $loc['placeholder_pixels'] ?>" name="margin" min="0" max="1024" value="<?= htmlspecialchars($params['margin']) ?>">
-					<datalist id="margins">
-						<option value="16">
-						<option value="32">
-						<option value="64">
-						<option value="128">
-					</datalist>
+					<input type="number" id="margin" placeholder="<?= $loc['placeholder_pixels'] ?>" name="margin" required="" min="0" max="1024" value="<?= htmlspecialchars($params['margin']) ?>">
 				</div>
 
 				<div class="param">
@@ -187,13 +181,7 @@ foreach($themeDimensionsIcons as $dimFav) // Set all icons dimensions
 							<?= $loc['help_size'] ?>
 						</p>
 					</details>
-					<input type="number" list="sizes" id="size" placeholder="<?= $loc['placeholder_pixels'] ?>" name="size" min="1" max="4096" value="<?= htmlspecialchars($params['size']) ?>">
-					<datalist id="sizes">
-						<option value="128">
-						<option value="256">
-						<option value="512">
-						<option value="1024">
-					</datalist>
+					<input type="number" id="size" placeholder="<?= $loc['placeholder_pixels'] ?>" name="size" required="" min="1" max="4096" value="<?= htmlspecialchars($params['size']) ?>">
 				</div>
 
 			</div>
@@ -257,6 +245,8 @@ if ($validFormSubmitted) {
 
 	$dataUri = $result->getDataUri();
 
+	$qrSize = $params['size'] + 2 * $params['margin'];
+
 ?>
 
 			<section id="output">