diff --git a/Tests/LibWeb/Layout/expected/block-and-inline/max-width-percentage-containing-block.txt b/Tests/LibWeb/Layout/expected/block-and-inline/max-width-percentage-containing-block.txt
new file mode 100644
index 0000000000..83b4949d31
--- /dev/null
+++ b/Tests/LibWeb/Layout/expected/block-and-inline/max-width-percentage-containing-block.txt
@@ -0,0 +1,14 @@
+Viewport <#document> at (0,0) content-size 800x600 children: not-inline
+ BlockContainer at (1,1) content-size 798x37.46875 [BFC] children: not-inline
+ BlockContainer
at (10,10) content-size 780x19.46875 children: not-inline
+ BlockContainer at (11,11) content-size 66.671875x17.46875 children: inline
+ line 0 width: 66.671875, height: 17.46875, bottom: 17.46875, baseline: 13.53125
+ frag 0 from TextNode start: 0, length: 7, rect: [11,11 66.671875x17.46875]
+ "Trimmed"
+ TextNode <#text>
+
+ViewportPaintable (Viewport<#document>) [0,0 800x600]
+ PaintableWithLines (BlockContainer) [0,0 800x39.46875]
+ PaintableWithLines (BlockContainer) [9,9 782x21.46875]
+ PaintableWithLines (BlockContainer.text) [10,10 68.671875x19.46875]
+ TextPaintable (TextNode<#text>)
diff --git a/Tests/LibWeb/Layout/expected/grid/min-max-content.txt b/Tests/LibWeb/Layout/expected/grid/min-max-content.txt
index d4ff025444..f7d48c8b5c 100644
--- a/Tests/LibWeb/Layout/expected/grid/min-max-content.txt
+++ b/Tests/LibWeb/Layout/expected/grid/min-max-content.txt
@@ -4,23 +4,23 @@ Viewport <#document> at (0,0) content-size 800x600 children: not-inline
Box at (8,8) content-size 784x17.46875 [GFC] children: not-inline
BlockContainer <(anonymous)> (not painted) [BFC] children: inline
TextNode <#text>
- BlockContainer at (8,8) content-size 46.890625x17.46875 [BFC] children: inline
+ BlockContainer at (8,8) content-size 196x17.46875 [BFC] children: inline
line 0 width: 93.765625, height: 17.46875, bottom: 17.46875, baseline: 13.53125
frag 0 from TextNode start: 0, length: 11, rect: [8,8 93.765625x17.46875]
"min-content"
TextNode <#text>
BlockContainer <(anonymous)> (not painted) [BFC] children: inline
TextNode <#text>
- BlockContainer at (54.890625,8) content-size 98.640625x17.46875 [BFC] children: inline
+ BlockContainer at (204,8) content-size 98.640625x17.46875 [BFC] children: inline
line 0 width: 98.640625, height: 17.46875, bottom: 17.46875, baseline: 13.53125
- frag 0 from TextNode start: 0, length: 11, rect: [54.890625,8 98.640625x17.46875]
+ frag 0 from TextNode start: 0, length: 11, rect: [204,8 98.640625x17.46875]
"max-content"
TextNode <#text>
BlockContainer <(anonymous)> (not painted) [BFC] children: inline
TextNode <#text>
- BlockContainer at (153.53125,8) content-size 638.46875x17.46875 [BFC] children: inline
+ BlockContainer at (302.640625,8) content-size 489.359375x17.46875 [BFC] children: inline
line 0 width: 21.609375, height: 17.46875, bottom: 17.46875, baseline: 13.53125
- frag 0 from TextNode start: 0, length: 3, rect: [153.53125,8 21.609375x17.46875]
+ frag 0 from TextNode start: 0, length: 3, rect: [302.640625,8 21.609375x17.46875]
"1fr"
TextNode <#text>
BlockContainer <(anonymous)> (not painted) [BFC] children: inline
@@ -30,9 +30,9 @@ ViewportPaintable (Viewport<#document>) [0,0 800x600]
PaintableWithLines (BlockContainer) [0,0 800x600]
PaintableWithLines (BlockContainer) [8,8 784x17.46875]
PaintableBox (Box.grid-container) [8,8 784x17.46875]
- PaintableWithLines (BlockContainer
.grid-item) [8,8 46.890625x17.46875] overflow: [8,8 93.765625x17.46875]
+ PaintableWithLines (BlockContainer
.grid-item) [8,8 196x17.46875]
TextPaintable (TextNode<#text>)
- PaintableWithLines (BlockContainer
.grid-item) [54.890625,8 98.640625x17.46875]
+ PaintableWithLines (BlockContainer
.grid-item) [204,8 98.640625x17.46875]
TextPaintable (TextNode<#text>)
- PaintableWithLines (BlockContainer
.grid-item) [153.53125,8 638.46875x17.46875]
+ PaintableWithLines (BlockContainer
.grid-item) [302.640625,8 489.359375x17.46875]
TextPaintable (TextNode<#text>)
diff --git a/Tests/LibWeb/Layout/input/block-and-inline/max-width-percentage-containing-block.html b/Tests/LibWeb/Layout/input/block-and-inline/max-width-percentage-containing-block.html
new file mode 100644
index 0000000000..352f959d1a
--- /dev/null
+++ b/Tests/LibWeb/Layout/input/block-and-inline/max-width-percentage-containing-block.html
@@ -0,0 +1,11 @@
+
Trimmed
\ No newline at end of file
diff --git a/Tests/LibWeb/Layout/input/grid/item-min-max-percentage-width.html b/Tests/LibWeb/Layout/input/grid/item-min-max-percentage-width.html
deleted file mode 100644
index 9559ea119a..0000000000
--- a/Tests/LibWeb/Layout/input/grid/item-min-max-percentage-width.html
+++ /dev/null
@@ -1,15 +0,0 @@
-
\ No newline at end of file
diff --git a/Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp b/Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp
index c568c84ea3..4f952c79d9 100644
--- a/Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp
+++ b/Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp
@@ -519,7 +519,10 @@ void BlockFormattingContext::layout_inline_children(BlockContainer const& block_
// NOTE: min-width or max-width for boxes with inline children can only be applied after inside layout
// is done and width of box content is known
auto used_width_px = context.automatic_content_width();
- auto available_width = AvailableSize::make_definite(used_width_px);
+ // https://www.w3.org/TR/css-sizing-3/#sizing-values
+ // Percentages are resolved against the width/height, as appropriate, of the box’s containing block.
+ auto containing_block_width = m_state.get(*block_container.containing_block()).content_width();
+ auto available_width = AvailableSize::make_definite(containing_block_width);
if (!should_treat_max_width_as_none(block_container, available_space.width)) {
auto max_width_px = calculate_inner_width(block_container, available_width, block_container.computed_values().max_width()).to_px(block_container);
if (used_width_px > max_width_px)