diff --git a/Userland/Libraries/LibWeb/CSS/Percentage.h b/Userland/Libraries/LibWeb/CSS/Percentage.h
index 68bb465728..e0716407ee 100644
--- a/Userland/Libraries/LibWeb/CSS/Percentage.h
+++ b/Userland/Libraries/LibWeb/CSS/Percentage.h
@@ -77,6 +77,15 @@ public:
     bool is_percentage() const { return m_value.template has<Percentage>(); }
     bool is_calculated() const { return m_value.template has<NonnullRefPtr<CalculatedStyleValue>>(); }
 
+    bool contains_percentage() const
+    {
+        if (is_percentage())
+            return true;
+        if (is_calculated())
+            return calculated()->contains_percentage();
+        return false;
+    }
+
     Percentage const& percentage() const
     {
         VERIFY(is_percentage());
diff --git a/Userland/Libraries/LibWeb/CSS/StyleValue.cpp b/Userland/Libraries/LibWeb/CSS/StyleValue.cpp
index 897209b0d3..b51e5cfd91 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleValue.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleValue.cpp
@@ -2054,4 +2054,51 @@ NonnullRefPtr<StyleValue> BorderRadiusStyleValue::absolutized(Gfx::IntRect const
     return BorderRadiusStyleValue::create(absolutized_horizontal_radius, absolutized_vertical_radius);
 }
 
+bool CalculatedStyleValue::contains_percentage() const
+{
+    return m_expression->contains_percentage();
+}
+
+bool CalculatedStyleValue::CalcSum::contains_percentage() const
+{
+    if (first_calc_product->contains_percentage())
+        return true;
+    for (auto& part : zero_or_more_additional_calc_products) {
+        if (part.contains_percentage())
+            return true;
+    }
+    return false;
+}
+
+bool CalculatedStyleValue::CalcSumPartWithOperator::contains_percentage() const
+{
+    return value->contains_percentage();
+}
+
+bool CalculatedStyleValue::CalcProduct::contains_percentage() const
+{
+    if (first_calc_value.contains_percentage())
+        return true;
+    for (auto& part : zero_or_more_additional_calc_values) {
+        if (part.contains_percentage())
+            return true;
+    }
+    return false;
+}
+
+bool CalculatedStyleValue::CalcProductPartWithOperator::contains_percentage() const
+{
+    return value.visit(
+        [](CalcValue const& value) { return value.contains_percentage(); },
+        [](CalcNumberValue const&) { return false; });
+}
+
+bool CalculatedStyleValue::CalcValue::contains_percentage() const
+{
+    return value.visit(
+        [](Percentage const&) { return true; },
+        [](NonnullOwnPtr<CalcSum> const& sum) { return sum->contains_percentage(); },
+        [](auto const&) { return false; });
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/CSS/StyleValue.h b/Userland/Libraries/LibWeb/CSS/StyleValue.h
index 5118c7a26a..ccfe444dbc 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleValue.h
+++ b/Userland/Libraries/LibWeb/CSS/StyleValue.h
@@ -609,6 +609,7 @@ public:
         String to_string() const;
         Optional<ResolvedType> resolved_type() const;
         CalculationResult resolve(Layout::Node const*, PercentageBasis const& percentage_basis) const;
+        bool contains_percentage() const;
     };
 
     // This represents that: https://www.w3.org/TR/css-values-3/#calc-syntax
@@ -623,6 +624,8 @@ public:
         String to_string() const;
         Optional<ResolvedType> resolved_type() const;
         CalculationResult resolve(Layout::Node const*, PercentageBasis const& percentage_basis) const;
+
+        bool contains_percentage() const;
     };
 
     struct CalcNumberSum {
@@ -645,6 +648,7 @@ public:
         String to_string() const;
         Optional<ResolvedType> resolved_type() const;
         CalculationResult resolve(Layout::Node const*, PercentageBasis const& percentage_basis) const;
+        bool contains_percentage() const;
     };
 
     struct CalcSumPartWithOperator {
@@ -658,6 +662,7 @@ public:
         String to_string() const;
         Optional<ResolvedType> resolved_type() const;
         CalculationResult resolve(Layout::Node const*, PercentageBasis const& percentage_basis) const;
+        bool contains_percentage() const;
     };
 
     struct CalcProductPartWithOperator {
@@ -667,6 +672,8 @@ public:
         String to_string() const;
         Optional<ResolvedType> resolved_type() const;
         CalculationResult resolve(Layout::Node const*, PercentageBasis const& percentage_basis) const;
+
+        bool contains_percentage() const;
     };
 
     struct CalcNumberProduct {
@@ -734,6 +741,8 @@ public:
     Optional<float> resolve_number();
     Optional<i64> resolve_integer();
 
+    bool contains_percentage() const;
+
 private:
     explicit CalculatedStyleValue(NonnullOwnPtr<CalcSum> calc_sum, ResolvedType resolved_type)
         : StyleValue(Type::Calculated)