diff --git a/Libraries/LibWeb/CSS/CalculatedOr.cpp b/Libraries/LibWeb/CSS/CalculatedOr.cpp
index f22d56f8940..5eb4485ae39 100644
--- a/Libraries/LibWeb/CSS/CalculatedOr.cpp
+++ b/Libraries/LibWeb/CSS/CalculatedOr.cpp
@@ -9,6 +9,7 @@
 #include <LibWeb/CSS/StyleValues/FlexStyleValue.h>
 #include <LibWeb/CSS/StyleValues/FrequencyStyleValue.h>
 #include <LibWeb/CSS/StyleValues/IntegerStyleValue.h>
+#include <LibWeb/CSS/StyleValues/KeywordStyleValue.h>
 #include <LibWeb/CSS/StyleValues/LengthStyleValue.h>
 #include <LibWeb/CSS/StyleValues/NumberStyleValue.h>
 #include <LibWeb/CSS/StyleValues/PercentageStyleValue.h>
@@ -67,6 +68,30 @@ NonnullRefPtr<StyleValue const> LengthOrCalculated::create_style_value() const
     return LengthStyleValue::create(value());
 }
 
+Optional<LengthOrAuto> LengthOrAutoOrCalculated::resolve_calculated(NonnullRefPtr<CalculatedStyleValue const> const& calculated, CalculationResolutionContext const& context) const
+{
+    return calculated->resolve_length(context).map([](auto& length) { return LengthOrAuto { length }; });
+}
+
+NonnullRefPtr<StyleValue const> LengthOrAutoOrCalculated::create_style_value() const
+{
+    auto const& length_or_auto = value();
+    if (length_or_auto.is_auto())
+        return KeywordStyleValue::create(Keyword::Auto);
+    return LengthStyleValue::create(length_or_auto.length());
+}
+
+bool LengthOrAutoOrCalculated::is_auto() const
+{
+    return !is_calculated() && value().is_auto();
+}
+
+LengthOrCalculated LengthOrAutoOrCalculated::without_auto() const
+{
+    VERIFY(!is_auto());
+    return value().length();
+}
+
 Optional<double> NumberOrCalculated::resolve_calculated(NonnullRefPtr<CalculatedStyleValue const> const& calculated, CalculationResolutionContext const& context) const
 {
     return calculated->resolve_number_deprecated(context);
diff --git a/Libraries/LibWeb/CSS/CalculatedOr.h b/Libraries/LibWeb/CSS/CalculatedOr.h
index 67b17d4bd0e..1323ddb6698 100644
--- a/Libraries/LibWeb/CSS/CalculatedOr.h
+++ b/Libraries/LibWeb/CSS/CalculatedOr.h
@@ -154,6 +154,16 @@ public:
     NonnullRefPtr<StyleValue const> create_style_value() const;
 };
 
+class LengthOrAutoOrCalculated : public CalculatedOr<LengthOrAutoOrCalculated, LengthOrAuto> {
+public:
+    using CalculatedOr::CalculatedOr;
+
+    Optional<LengthOrAuto> resolve_calculated(NonnullRefPtr<CalculatedStyleValue const> const&, CalculationResolutionContext const&) const;
+    NonnullRefPtr<StyleValue const> create_style_value() const;
+    bool is_auto() const;
+    LengthOrCalculated without_auto() const;
+};
+
 class NumberOrCalculated : public CalculatedOr<NumberOrCalculated, double> {
 public:
     using CalculatedOr::CalculatedOr;
diff --git a/Libraries/LibWeb/Forward.h b/Libraries/LibWeb/Forward.h
index 3a7531a6ae8..d500b4c516d 100644
--- a/Libraries/LibWeb/Forward.h
+++ b/Libraries/LibWeb/Forward.h
@@ -311,6 +311,7 @@ class KeywordStyleValue;
 class Length;
 class LengthBox;
 class LengthOrAuto;
+class LengthOrAutoOrCalculated;
 class LengthOrCalculated;
 class LengthPercentage;
 class LengthStyleValue;