diff --git a/src/Twig/Functions/IconExtension.php b/src/Twig/Functions/IconExtension.php
index b092417..f39e842 100644
--- a/src/Twig/Functions/IconExtension.php
+++ b/src/Twig/Functions/IconExtension.php
@@ -9,13 +9,16 @@ use Twig\TwigFunction;
 
 final class IconExtension extends AbstractExtension
 {
-    public function __construct(private array $directories) {}
+    public const DEFAULT_SIZE = 32;
 
     private const DEFAULT_OPTIONS = [
         'icon' => null,
         'title' => null,
+        'size' => self::DEFAULT_SIZE
     ];
 
+    public function __construct(private array $directories) {}
+
     /**
      * @inheritDoc
      */
@@ -30,6 +33,7 @@ final class IconExtension extends AbstractExtension
 
     /**
      * @param array $options
+     * [ options here ]
      */
     public function renderIcon(array $userOptions): string
     {
@@ -43,6 +47,16 @@ final class IconExtension extends AbstractExtension
             $markup = $this->addTitleToMarkup($cleanSvgMarkup, $options['title']);
         }
 
+        if ($options['size'] < 0)
+            throw new \InvalidArgumentException('Size must not be negative');
+
+        if (!is_int($options['size']))
+            throw new \TypeError('Size value must be an integer');
+
+
+        $markup = $this->setSize($markup, $options['size']);
+
+
         return $markup;
     }
 
@@ -87,12 +101,35 @@ final class IconExtension extends AbstractExtension
 
     private function addTitleToMarkup(string $markup, ?string $title): string
     {
-        if (null === $title) {
+        if (null === $title)
             return $markup;
-        }
 
         return preg_replace('/(<svg(.|\n)*?>\n?)/', "$1<title>$title</title>", $markup);
     }
+
+    private function setSize(string $content, int $size): string
+    {
+        $svgAsXmlElement = new \SimpleXMLElement($content);
+        $svgAsXmlElement = $this->addAttributeToXmlElement($svgAsXmlElement, 'width', $size);
+        $svgAsXmlElement = $this->addAttributeToXmlElement($svgAsXmlElement, 'height', $size);
+        return $this->removeXMLDeclaration($svgAsXmlElement->saveXML());
+    }
+
+    private function removeXMLDeclaration(string $content): string
+    {
+        return trim(preg_replace('/<\?xml.*\?>/', '', $content));
+    }
+
+    private function addAttributeToXmlElement(\SimpleXMLElement $xml, string $attrName, mixed $attrValue): \SimpleXMLElement
+    {
+        if (isset($xml->attributes()->$attrName)) {
+            $xml->attributes()->$attrName = strval($attrValue);
+        } else {
+            $xml->addAttribute($attrName, strval($attrValue));
+        }
+
+        return $xml;
+    }
 }
 
 class IconNotFound extends \Exception {};
diff --git a/tests/Twig/Functions/IconExtensionTest.php b/tests/Twig/Functions/IconExtensionTest.php
index 50a48d4..e633c39 100644
--- a/tests/Twig/Functions/IconExtensionTest.php
+++ b/tests/Twig/Functions/IconExtensionTest.php
@@ -71,4 +71,76 @@ class IconExtensionTest extends TestCase
         $this->expectException(\InvalidArgumentException::class);
         $this->icon->renderIcon(['icon' => self::ICON, 'title' => '']);
     }
+
+    public function testThrowsWhenPassedNegativeSizeValue(): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->icon->renderIcon(['icon' => self::ICON, 'size' => -1]);
+    }
+
+    public function testThrowsWhenSizeIsNotAnInt(): void
+    {
+        $this->expectException(\TypeError::class);
+        $this->icon->renderIcon(['icon' => self::ICON, 'size' => 1.0]);
+    }
+
+    public function testSvgWidthIsSet(): void
+    {
+        $regex = '/^<svg.+?width="99"/';
+        $content = $this->icon->renderIcon(['icon' => self::ICON, 'size' => 99]);
+        $this->assertMatchesRegularExpression($regex, $content);
+    }
+
+    public function testSvgHeightIsSet(): void
+    {
+        $regex = '/^<svg.+?width="99"/';
+        $content = $this->icon->renderIcon(['icon' => self::ICON, 'size' => 99]);
+        $this->assertMatchesRegularExpression($regex, $content);
+    }
+
+    public function testNoXmlDeclarationIsAdded(): void
+    {
+        $content = $this->icon->renderIcon(['icon' => self::ICON, 'size' => 99]);
+        $this->assertStringNotContainsString('<xml', $content);
+    }
+
+    public function testOnlyOneWidthAttributeIsSet(): void
+    {
+        $content = $this->icon->renderIcon(['icon' => self::ICON, 'size' => 99]);
+        $timesMatched = preg_match_all('/width="99"/', $content);
+        $this->assertSame(1, $timesMatched);
+    }
+
+    public function testOnlyOneHeightAttributeIsSet(): void
+    {
+        $content = $this->icon->renderIcon(['icon' => self::ICON, 'size' => 99]);
+        $timesMatched = preg_match_all('/height="99"/', $content);
+        $this->assertSame(1, $timesMatched);
+    }
+
+    public function testDefaultSizeIsSetOnSvgIfNoSizeOptionPassed(): void
+    {
+        $defaultSize = IconExtension::DEFAULT_SIZE;
+        $content = $this->icon->renderIcon(['icon' => self::ICON]);
+
+        $regex = "/^<svg.+?width=\"{$defaultSize}\"/";
+        $this->assertMatchesRegularExpression($regex, $content);
+
+        $regex = "/^<svg.+?height=\"{$defaultSize}\"/";
+        $this->assertMatchesRegularExpression($regex, $content);
+    }
+
+    public function testDefaultSizeIsOnlySetOnce(): void
+    {
+        $defaultSize = IconExtension::DEFAULT_SIZE;
+        $content = $this->icon->renderIcon(['icon' => self::ICON]);
+
+        $widthRegex = "/width=\"{$defaultSize}\"/";
+        $timesMatched = preg_match_all($widthRegex, $content);
+        $this->assertSame(1, $timesMatched);
+
+        $heightRegex = "/height=\"{$defaultSize}\"/";
+        $timesMatched = preg_match_all($heightRegex, $content);
+        $this->assertSame(1, $timesMatched);
+    }
 }
diff --git a/tests/icons/test.svg b/tests/icons/test.svg
index 2c9ec70..0296bda 100644
--- a/tests/icons/test.svg
+++ b/tests/icons/test.svg
@@ -1,5 +1,5 @@
 <svg xmlns="http://www.w3.org/2000/svg" width="512" height="512" viewBox="96 96 320 320">
     <title>Some cross lol</title>
-    <line x1="256" y1="112" x2="256" y2="400" style="fill: none; stroke: rgb(0,0, 0); stroke-linecap: round; stroke-linejoin: round; stroke-width: 32px;"></line>
-    <line x1="400" y1="256" x2="112" y2="256" style="fill: none; stroke: #000; stroke-linecap: round; stroke-linejoin: round; stroke-width: 32px;"></line>
+    <line x1="256" y1="112" x2="256" y2="400" width="101" height="101" style="fill: none; stroke: rgb(0,0, 0); stroke-linecap: round; stroke-linejoin: round; stroke-width: 32px;"></line>
+    <line x1="400" y1="256" x2="112" y2="256" width="102" height="102" style="fill: none; stroke: #000; stroke-linecap: round; stroke-linejoin: round; stroke-width: 32px;"></line>
 </svg>