diff --git a/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp b/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp
index 900384f994..4b5b149582 100644
--- a/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp
+++ b/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp
@@ -168,6 +168,8 @@ static NonnullRefPtr<StyleValue const> style_value_for_size(CSS::Size const& siz
         return LengthStyleValue::create(size.length());
     if (size.is_auto())
         return IdentifierStyleValue::create(ValueID::Auto);
+    if (size.is_calculated())
+        return size.calculated();
     if (size.is_min_content())
         return IdentifierStyleValue::create(ValueID::MinContent);
     if (size.is_max_content())
diff --git a/Userland/Libraries/LibWeb/CSS/Size.cpp b/Userland/Libraries/LibWeb/CSS/Size.cpp
index 9b6ea918eb..fa4e8f8fe9 100644
--- a/Userland/Libraries/LibWeb/CSS/Size.cpp
+++ b/Userland/Libraries/LibWeb/CSS/Size.cpp
@@ -41,6 +41,11 @@ Size Size::make_percentage(Percentage percentage)
     return Size { Type::Percentage, move(percentage) };
 }
 
+Size Size::make_calculated(NonnullRefPtr<Web::CSS::CalculatedStyleValue> calculated)
+{
+    return Size { Type::Calculated, move(calculated) };
+}
+
 Size Size::make_min_content()
 {
     return Size { Type::MinContent, Length::make_auto() };
@@ -79,6 +84,7 @@ ErrorOr<String> Size::to_string() const
     switch (m_type) {
     case Type::Auto:
         return "auto"_string;
+    case Type::Calculated:
     case Type::Length:
     case Type::Percentage:
         return m_length_percentage.to_string();
diff --git a/Userland/Libraries/LibWeb/CSS/Size.h b/Userland/Libraries/LibWeb/CSS/Size.h
index d8cad444a1..8e2a8ac952 100644
--- a/Userland/Libraries/LibWeb/CSS/Size.h
+++ b/Userland/Libraries/LibWeb/CSS/Size.h
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -15,6 +16,7 @@ class Size {
 public:
     enum class Type {
         Auto,
+        Calculated,
         Length,
         Percentage,
         MinContent,
@@ -27,12 +29,14 @@ public:
     static Size make_px(CSSPixels);
     static Size make_length(Length);
     static Size make_percentage(Percentage);
+    static Size make_calculated(NonnullRefPtr<CalculatedStyleValue>);
     static Size make_min_content();
     static Size make_max_content();
     static Size make_fit_content(Length available_space);
     static Size make_none();
 
     bool is_auto() const { return m_type == Type::Auto; }
+    bool is_calculated() const { return m_type == Type::Calculated; }
     bool is_length() const { return m_type == Type::Length; }
     bool is_percentage() const { return m_type == Type::Percentage; }
     bool is_min_content() const { return m_type == Type::MinContent; }
@@ -45,6 +49,12 @@ public:
 
     bool contains_percentage() const;
 
+    CalculatedStyleValue const& calculated() const
+    {
+        VERIFY(is_calculated());
+        return m_length_percentage.calculated();
+    }
+
     CSS::Length const& length() const
     {
         VERIFY(is_length());
diff --git a/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp b/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
index ded4425ebb..eadfa46b1a 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
@@ -79,7 +79,7 @@ CSS::Size StyleProperties::size_value(CSS::PropertyID id) const
     }
 
     if (value->is_calculated())
-        return CSS::Size::make_length(CSS::Length::make_calculated(const_cast<CalculatedStyleValue&>(value->as_calculated())));
+        return CSS::Size::make_calculated(const_cast<CalculatedStyleValue&>(value->as_calculated()));
 
     if (value->is_percentage())
         return CSS::Size::make_percentage(value->as_percentage().percentage());