diff --git a/Libraries/LibWeb/Layout/LineBox.cpp b/Libraries/LibWeb/Layout/LineBox.cpp
index 82f743e1468..84467e40c63 100644
--- a/Libraries/LibWeb/Layout/LineBox.cpp
+++ b/Libraries/LibWeb/Layout/LineBox.cpp
@@ -5,7 +5,6 @@
  */
 
 #include <AK/CharacterTypes.h>
-#include <AK/TypeCasts.h>
 #include <AK/Utf8View.h>
 #include <LibWeb/DOM/Position.h>
 #include <LibWeb/Layout/Box.h>
@@ -54,50 +53,70 @@ void LineBox::add_fragment(Node const& layout_node, int start, int length, CSSPi
     m_block_length = max(m_block_length, content_height + border_box_top + border_box_bottom);
 }
 
-void LineBox::trim_trailing_whitespace()
+CSSPixels LineBox::calculate_or_trim_trailing_whitespace(RemoveTrailingWhitespace should_remove)
 {
     auto should_trim = [](LineBoxFragment* fragment) {
         auto ws = fragment->layout_node().computed_values().white_space();
         return ws == CSS::WhiteSpace::Normal || ws == CSS::WhiteSpace::Nowrap || ws == CSS::WhiteSpace::PreLine;
     };
 
+    CSSPixels whitespace_width = 0;
     LineBoxFragment* last_fragment = nullptr;
+    size_t fragment_index = m_fragments.size();
     for (;;) {
-        if (m_fragments.is_empty())
-            return;
-        // last_fragment cannot be null from here on down, as m_fragments is not empty.
-        last_fragment = &m_fragments.last();
+        if (fragment_index == 0)
+            return whitespace_width;
+
+        last_fragment = &m_fragments[--fragment_index];
         auto const* dom_node = last_fragment->layout_node().dom_node();
         if (dom_node) {
             auto cursor_position = dom_node->document().cursor_position();
             if (cursor_position && cursor_position->node() == dom_node)
-                return;
+                return whitespace_width;
         }
         if (!should_trim(last_fragment))
-            return;
-        if (last_fragment->is_justifiable_whitespace()) {
-            m_inline_length -= last_fragment->inline_length();
-            m_fragments.remove(m_fragments.size() - 1);
-        } else {
+            return whitespace_width;
+        if (!last_fragment->is_justifiable_whitespace())
             break;
+
+        whitespace_width += last_fragment->inline_length();
+        if (should_remove == RemoveTrailingWhitespace::Yes) {
+            m_inline_length -= last_fragment->inline_length();
+            m_fragments.remove(fragment_index);
         }
     }
 
     auto last_text = last_fragment->text();
     if (last_text.is_null())
-        return;
+        return whitespace_width;
 
-    while (last_fragment->length()) {
-        auto last_character = last_text[last_fragment->length() - 1];
+    size_t last_fragment_length = last_fragment->length();
+    while (last_fragment_length) {
+        auto last_character = last_text[--last_fragment_length];
         if (!is_ascii_space(last_character))
             break;
 
         auto const& font = last_fragment->glyph_run() ? last_fragment->glyph_run()->font() : last_fragment->layout_node().first_available_font();
         int last_character_width = font.glyph_width(last_character);
-        last_fragment->m_length -= 1;
-        last_fragment->set_inline_length(last_fragment->inline_length() - last_character_width);
-        m_inline_length -= last_character_width;
+        whitespace_width += last_character_width;
+        if (should_remove == RemoveTrailingWhitespace::Yes) {
+            last_fragment->m_length -= 1;
+            last_fragment->set_inline_length(last_fragment->inline_length() - last_character_width);
+            m_inline_length -= last_character_width;
+        }
     }
+
+    return whitespace_width;
+}
+
+CSSPixels LineBox::get_trailing_whitespace_width() const
+{
+    return const_cast<LineBox&>(*this).calculate_or_trim_trailing_whitespace(RemoveTrailingWhitespace::No);
+}
+
+void LineBox::trim_trailing_whitespace()
+{
+    calculate_or_trim_trailing_whitespace(RemoveTrailingWhitespace::Yes);
 }
 
 bool LineBox::is_empty_or_ends_in_whitespace() const
diff --git a/Libraries/LibWeb/Layout/LineBox.h b/Libraries/LibWeb/Layout/LineBox.h
index 0f22a5e39d6..2daf8473be7 100644
--- a/Libraries/LibWeb/Layout/LineBox.h
+++ b/Libraries/LibWeb/Layout/LineBox.h
@@ -32,6 +32,7 @@ public:
     Vector<LineBoxFragment> const& fragments() const { return m_fragments; }
     Vector<LineBoxFragment>& fragments() { return m_fragments; }
 
+    CSSPixels get_trailing_whitespace_width() const;
     void trim_trailing_whitespace();
 
     bool is_empty_or_ends_in_whitespace() const;
@@ -44,6 +45,13 @@ private:
     friend class InlineFormattingContext;
     friend class LineBuilder;
 
+    enum class RemoveTrailingWhitespace : u8 {
+        Yes,
+        No,
+    };
+
+    CSSPixels calculate_or_trim_trailing_whitespace(RemoveTrailingWhitespace);
+
     Vector<LineBoxFragment> m_fragments;
     CSSPixels m_inline_length { 0 };
     CSSPixels m_block_length { 0 };
diff --git a/Libraries/LibWeb/Layout/LineBuilder.cpp b/Libraries/LibWeb/Layout/LineBuilder.cpp
index 4268931db31..60d53e4d98b 100644
--- a/Libraries/LibWeb/Layout/LineBuilder.cpp
+++ b/Libraries/LibWeb/Layout/LineBuilder.cpp
@@ -117,10 +117,14 @@ CSSPixels LineBuilder::y_for_float_to_be_inserted_here(Box const& box)
 
     CSSPixels candidate_block_offset = m_current_block_offset;
 
+    // Determine the current line width and subtract trailing whitespace, since those have not yet been removed while
+    // placing floating boxes.
     auto const& current_line = ensure_last_line_box();
+    auto current_line_width = current_line.width() - current_line.get_trailing_whitespace_width();
+
     // If there's already inline content on the current line, check if the new float can fit
     // alongside the content. If not, place it on the next line.
-    if (current_line.width() > 0 && (current_line.width() + width) > m_available_width_for_current_line)
+    if (current_line_width > 0 && (current_line_width + width) > m_available_width_for_current_line)
         candidate_block_offset += current_line.height();
 
     // Then, look for the next Y position where we can fit the new float.
diff --git a/Tests/LibWeb/Layout/expected/block-and-inline/float-following-trailing-whitespace.txt b/Tests/LibWeb/Layout/expected/block-and-inline/float-following-trailing-whitespace.txt
new file mode 100644
index 00000000000..38a71a32976
--- /dev/null
+++ b/Tests/LibWeb/Layout/expected/block-and-inline/float-following-trailing-whitespace.txt
@@ -0,0 +1,28 @@
+Viewport <#document> at (0,0) content-size 800x600 children: not-inline
+  BlockContainer <html> at (0,0) content-size 800x33 [BFC] children: not-inline
+    BlockContainer <body> at (8,8) content-size 784x17 children: not-inline
+      BlockContainer <div.a> at (8,8) content-size 100x17 children: inline
+        frag 0 from BlockContainer start: 0, length: 0, rect: [8,8 50x17] baseline: 13.296875
+        TextNode <#text>
+        BlockContainer <div.b> at (8,8) content-size 50x17 inline-block [BFC] children: inline
+          frag 0 from TextNode start: 0, length: 3, rect: [8,8 27.15625x17] baseline: 13.296875
+              "foo"
+          TextNode <#text>
+        TextNode <#text>
+        BlockContainer <div.c> at (58,8) content-size 50x17 floating [BFC] children: inline
+          frag 0 from TextNode start: 0, length: 3, rect: [58,8 27.640625x17] baseline: 13.296875
+              "bar"
+          TextNode <#text>
+        TextNode <#text>
+      BlockContainer <(anonymous)> at (8,25) content-size 784x0 children: inline
+        TextNode <#text>
+
+ViewportPaintable (Viewport<#document>) [0,0 800x600]
+  PaintableWithLines (BlockContainer<HTML>) [0,0 800x33]
+    PaintableWithLines (BlockContainer<BODY>) [8,8 784x17]
+      PaintableWithLines (BlockContainer<DIV>.a) [8,8 100x17]
+        PaintableWithLines (BlockContainer<DIV>.b) [8,8 50x17]
+          TextPaintable (TextNode<#text>)
+        PaintableWithLines (BlockContainer<DIV>.c) [58,8 50x17]
+          TextPaintable (TextNode<#text>)
+      PaintableWithLines (BlockContainer(anonymous)) [8,25 784x0]
diff --git a/Tests/LibWeb/Layout/input/block-and-inline/float-following-trailing-whitespace.html b/Tests/LibWeb/Layout/input/block-and-inline/float-following-trailing-whitespace.html
new file mode 100644
index 00000000000..3696f1ca3e1
--- /dev/null
+++ b/Tests/LibWeb/Layout/input/block-and-inline/float-following-trailing-whitespace.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<style>
+    .a {
+        background-color: red;
+        width: 100px;
+    }
+    .b {
+        background-color: green;
+        display: inline-block;
+        width: 50px;
+    }
+    .c {
+        background-color: blue;
+        float: right;
+        width: 50px;
+    }
+</style>
+<div class="a">
+    <div class="b">foo</div>
+    <div class="c">bar</div>
+</div>