diff --git a/AK/StringBuilder.cpp b/AK/StringBuilder.cpp
index 0a363a5355..7a76fcae33 100644
--- a/AK/StringBuilder.cpp
+++ b/AK/StringBuilder.cpp
@@ -18,7 +18,7 @@ namespace AK {
 
 inline void StringBuilder::will_append(size_t size)
 {
-    Checked<size_t> needed_capacity = m_length;
+    Checked<size_t> needed_capacity = m_buffer.size();
     needed_capacity += size;
     VERIFY(!needed_capacity.has_overflow());
     // Prefer to completely use the existing capacity first
@@ -41,7 +41,6 @@ void StringBuilder::append(const StringView& str)
         return;
     will_append(str.length());
     m_buffer.append(str.characters_without_null_termination(), str.length());
-    m_length += str.length();
 }
 
 void StringBuilder::append(const char* characters, size_t length)
@@ -53,7 +52,6 @@ void StringBuilder::append(char ch)
 {
     will_append(1);
     m_buffer.append(&ch, 1);
-    m_length += 1;
 }
 
 void StringBuilder::appendvf(const char* fmt, va_list ap)
@@ -83,13 +81,12 @@ String StringBuilder::build() const
 
 StringView StringBuilder::string_view() const
 {
-    return StringView { data(), m_length };
+    return StringView { data(), m_buffer.size() };
 }
 
 void StringBuilder::clear()
 {
     m_buffer.clear();
-    m_length = 0;
 }
 
 void StringBuilder::append_code_point(u32 code_point)
diff --git a/AK/StringBuilder.h b/AK/StringBuilder.h
index bc0470a211..118e5c0958 100644
--- a/AK/StringBuilder.h
+++ b/AK/StringBuilder.h
@@ -44,9 +44,9 @@ public:
     [[nodiscard]] StringView string_view() const;
     void clear();
 
-    [[nodiscard]] size_t length() const { return m_length; }
-    [[nodiscard]] bool is_empty() const { return m_length == 0; }
-    void trim(size_t count) { m_length -= count; }
+    [[nodiscard]] size_t length() const { return m_buffer.size(); }
+    [[nodiscard]] bool is_empty() const { return m_buffer.is_empty(); }
+    void trim(size_t count) { m_buffer.resize(m_buffer.size() - count); }
 
     template<class SeparatorType, class CollectionType>
     void join(const SeparatorType& separator, const CollectionType& collection)
@@ -68,7 +68,6 @@ private:
 
     static constexpr size_t inline_capacity = 128;
     AK::Detail::ByteBuffer<inline_capacity> m_buffer;
-    size_t m_length { 0 };
 };
 
 }