diff --git a/openpdf/src/main/java/com/lowagie/text/html/FontSize.java b/openpdf/src/main/java/com/lowagie/text/html/FontSize.java
new file mode 100644
index 000000000..b6ddad93b
--- /dev/null
+++ b/openpdf/src/main/java/com/lowagie/text/html/FontSize.java
@@ -0,0 +1,57 @@
+package com.lowagie.text.html;
+
+/**
+ * Named font sizes defined by CSS
+ * <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/font-size">font-size</a> property
+ */
+public enum FontSize {
+
+    // Absolute-size keywords, based on the user's default font size (which is medium).
+    XX_SMALL("xx-small", 0.6f, false),
+    X_SMALL("x-small", 0.75f, false),
+    SMALL("small", 0.89f, false),
+    MEDIUM("medium", 1.0f, false),
+    LARGE("large", 1.2f, false),
+    X_LARGE("x-large", 1.5f, false),
+    XX_LARGE("xx-large", 2.0f, false),
+    XXX_LARGE("xxx-large", 2.5f, false),
+
+    // Relative-size keywords. The font will be larger or smaller relative to the parent element's font size,
+    // roughly by the ratio used to separate the absolute-size keywords above.
+    SMALLER("smaller", 0.89f, true),
+    LARGER("larger", 1.2f, true);
+
+    private final float scale;
+    private final String textValue;
+    private final boolean relative;
+
+    FontSize(String textValue, float scale, boolean relative) {
+        this.textValue = textValue;
+        this.scale = scale;
+        this.relative = relative;
+    }
+
+    public String getTextValue() {
+        return textValue;
+    }
+
+    public float getScale() {
+        return scale;
+    }
+
+    public boolean isRelative() {
+        return relative;
+    }
+
+    public static FontSize parse(String text) {
+        if (text == null || text.isEmpty() || !Character.isLetter(text.charAt(0))) {
+            return null;
+        }
+        for (FontSize fontSize : values()) {
+            if (fontSize.getTextValue().equalsIgnoreCase(text)) {
+                return fontSize;
+            }
+        }
+        return null;
+    }
+}
diff --git a/openpdf/src/main/java/com/lowagie/text/html/Markup.java b/openpdf/src/main/java/com/lowagie/text/html/Markup.java
index c36f3187e..5c2b4a82a 100644
--- a/openpdf/src/main/java/com/lowagie/text/html/Markup.java
+++ b/openpdf/src/main/java/com/lowagie/text/html/Markup.java
@@ -479,6 +479,15 @@ public static float parseLength(String string, float actualFontSize) {
         if (string == null) {
             return 0f;
         }
+        FontSize fs = FontSize.parse(string);// it can be one of the CCS font size names (e.g. 'x-large')
+        if (fs != null) {
+            if (fs.isRelative()) {
+                return fs.getScale() * actualFontSize;
+            } else {
+                return fs.getScale() * DEFAULT_FONT_SIZE;
+            }
+        }
+
         int pos = 0;
         int length = string.length();
         boolean ok = true;
diff --git a/openpdf/src/test/java/com/lowagie/text/html/FontSizeTest.java b/openpdf/src/test/java/com/lowagie/text/html/FontSizeTest.java
index 86d3f151a..e645bfc06 100644
--- a/openpdf/src/test/java/com/lowagie/text/html/FontSizeTest.java
+++ b/openpdf/src/test/java/com/lowagie/text/html/FontSizeTest.java
@@ -11,6 +11,7 @@
 import com.lowagie.text.pdf.PdfWriter;
 import java.io.StringReader;
 import java.nio.file.Files;
+import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.HashMap;
 import java.util.List;
@@ -52,4 +53,62 @@ void testFontSize() throws Exception {
         Chunk chunk5 = (Chunk) paragraph.get(4);
         Assertions.assertEquals(0.5 * defaultFontSize, chunk5.getFont().getSize());
     }
+
+    @Test
+    void testNamedFontSize() throws Exception {
+        StringReader reader = new StringReader(
+            "<span style=\"font-size:20pt\">" +
+                "<span style=\"font-size:xx-small\">Text xx-small</span><br/>" +
+                "<span style=\"font-size:x-small\">Text x-small</span><br/>" +
+                "<span style=\"font-size:small\">Text small</span><br/>" +
+                "<span style=\"font-size:medium\">Text medium</span><br/>" +
+                "<span style=\"font-size:large\">Text large</span><br/>" +
+                "<span style=\"font-size:x-large\">Text x-large</span><br/>" +
+                "<span style=\"font-size:xx-large\">Text xx-large</span><br/>" +
+                "<span style=\"font-size:xxx-large\">Text xxx-large</span><br/>" +
+                "</span>" +
+
+                "<span style=\"font-size:20pt\">" +
+                "<span style=\"font-size:smaller\">Text smaller</span><br/>" +
+                "<span style=\"font-size:larger\">Text larger</span><br/>" +
+                "</span>"
+        );
+        StyleSheet styleSheet = new StyleSheet();
+        Map<String, Object> interfaceProps = new HashMap<>();
+        List<Element> elements = HTMLWorker.parseToList(reader, styleSheet, interfaceProps);
+
+        Document document = new Document();
+        PdfWriter instance = PdfWriter.getInstance(document,
+            Files.newOutputStream(Path.of("target/Font Size Named.pdf")));
+        document.open();
+        instance.getInfo().put(PdfName.CREATOR, new PdfString(Document.getVersion()));
+        for (Element e : elements) {
+            document.add(e);
+        }
+        document.close();
+
+        int i = 0;
+        Paragraph paragraph = (Paragraph) elements.get(0);
+        Chunk chunk1 = (Chunk) paragraph.get((i++) * 2);
+        Assertions.assertEquals(FontSize.XX_SMALL.getScale() * Markup.DEFAULT_FONT_SIZE, chunk1.getFont().getSize());
+        Chunk chunk2 = (Chunk) paragraph.get((i++) * 2);
+        Assertions.assertEquals(FontSize.X_SMALL.getScale() * Markup.DEFAULT_FONT_SIZE, chunk2.getFont().getSize());
+        Chunk chunk3 = (Chunk) paragraph.get((i++) * 2);
+        Assertions.assertEquals(FontSize.SMALL.getScale() * Markup.DEFAULT_FONT_SIZE, chunk3.getFont().getSize());
+        Chunk chunk4 = (Chunk) paragraph.get((i++) * 2);
+        Assertions.assertEquals(FontSize.MEDIUM.getScale() * Markup.DEFAULT_FONT_SIZE, chunk4.getFont().getSize());
+        Chunk chunk5 = (Chunk) paragraph.get((i++) * 2);
+        Assertions.assertEquals(FontSize.LARGE.getScale() * Markup.DEFAULT_FONT_SIZE, chunk5.getFont().getSize());
+        Chunk chunk6 = (Chunk) paragraph.get((i++) * 2);
+        Assertions.assertEquals(FontSize.X_LARGE.getScale() * Markup.DEFAULT_FONT_SIZE, chunk6.getFont().getSize());
+        Chunk chunk7 = (Chunk) paragraph.get((i++) * 2);
+        Assertions.assertEquals(FontSize.XX_LARGE.getScale() * Markup.DEFAULT_FONT_SIZE, chunk7.getFont().getSize());
+        Chunk chunk8 = (Chunk) paragraph.get((i++) * 2);
+        Assertions.assertEquals(FontSize.XXX_LARGE.getScale() * Markup.DEFAULT_FONT_SIZE, chunk8.getFont().getSize());
+
+        Chunk chunk9 = (Chunk) paragraph.get((i++) * 2);
+        Assertions.assertEquals(FontSize.SMALLER.getScale() * 20f, chunk9.getFont().getSize());
+        Chunk chunk10 = (Chunk) paragraph.get((i++) * 2);
+        Assertions.assertEquals(FontSize.LARGER.getScale() * 20f, chunk10.getFont().getSize());
+    }
 }