diff --git a/packages/super-editor/src/core/super-converter/v3/handlers/utils.js b/packages/super-editor/src/core/super-converter/v3/handlers/utils.js
index 9023c34e11..fa6ebe0205 100644
--- a/packages/super-editor/src/core/super-converter/v3/handlers/utils.js
+++ b/packages/super-editor/src/core/super-converter/v3/handlers/utils.js
@@ -113,6 +113,36 @@ export function createTrackChangesPropertyHandler(xmlName, sdName = null, extraA
   };
 }
 
+/**
+ * Parses a measurement value, handling ECMA-376 percentage strings.
+ *
+ * Per ECMA-376 §17.18.90 (ST_TblWidth): when type="pct" and value contains "%",
+ * it should be interpreted as a whole percentage point (e.g., "100%" = 100%).
+ * Otherwise, percentages are in fiftieths (5000 = 100%).
+ *
+ * @param {any} value The raw value from w:w attribute
+ * @param {string|undefined} type The type from w:type attribute
+ * @returns {number|undefined} The parsed value, converted to fiftieths if needed
+ */
+export const parseMeasurementValue = (value, type) => {
+  if (value == null) return undefined;
+  const strValue = String(value);
+
+  // Per ECMA-376 §17.18.90: when type="pct" and value contains "%",
+  // interpret as whole percentage and convert to fiftieths format
+  if (type === 'pct' && strValue.includes('%')) {
+    const percent = parseFloat(strValue);
+    if (!isNaN(percent)) {
+      // Convert whole percentage to OOXML fiftieths (100% → 5000)
+      return Math.round(percent * 50);
+    }
+  }
+
+  // Standard integer parsing for numeric values
+  const intValue = parseInt(strValue, 10);
+  return isNaN(intValue) ? undefined : intValue;
+};
+
 /**
  * Helper to create property handlers for measurement attributes (CT_TblWidth => w:w and w:type)
  * @param {string} xmlName The XML attribute name (with namespace).
@@ -124,12 +154,14 @@ export function createMeasurementPropertyHandler(xmlName, sdName = null) {
   return {
     xmlName,
     sdNodeOrKeyName: sdName,
-    attributes: [
-      createAttributeHandler('w:w', 'value', parseInteger, integerToString),
-      createAttributeHandler('w:type'),
-    ],
-    encode: (_, encodedAttrs) => {
-      return encodedAttrs['value'] != null ? encodedAttrs : undefined;
+    attributes: [createAttributeHandler('w:w', 'value', (v) => v, integerToString), createAttributeHandler('w:type')],
+    encode: (params, encodedAttrs) => {
+      // Parse the value with type context for ECMA-376 percentage string handling
+      const rawValue = encodedAttrs['value'];
+      const type = encodedAttrs['type'];
+      const parsedValue = parseMeasurementValue(rawValue, type);
+      if (parsedValue == null) return undefined;
+      return { ...encodedAttrs, value: parsedValue };
     },
     decode: function ({ node }) {
       const decodedAttrs = this.decodeAttributes({ node: { ...node, attrs: node.attrs[sdName] || {} } });
diff --git a/packages/super-editor/src/core/super-converter/v3/handlers/w/tblW/tblW-translator.test.js b/packages/super-editor/src/core/super-converter/v3/handlers/w/tblW/tblW-translator.test.js
index 9af7b6dae6..fbd878e570 100644
--- a/packages/super-editor/src/core/super-converter/v3/handlers/w/tblW/tblW-translator.test.js
+++ b/packages/super-editor/src/core/super-converter/v3/handlers/w/tblW/tblW-translator.test.js
@@ -18,6 +18,43 @@ describe('w:tblW translator', () => {
       expect(result.value).toBe(150);
     });
 
+    // SD-1633: ECMA-376 percentage string handling
+    it('converts percentage string "100%" with type="pct" to fiftieths (5000)', () => {
+      const result = translator.encode({
+        nodes: [{ attributes: { 'w:w': '100%', 'w:type': 'pct' } }],
+      });
+      expect(result).toEqual({ value: 5000, type: 'pct' });
+    });
+
+    it('converts percentage string "50%" with type="pct" to fiftieths (2500)', () => {
+      const result = translator.encode({
+        nodes: [{ attributes: { 'w:w': '50%', 'w:type': 'pct' } }],
+      });
+      expect(result).toEqual({ value: 2500, type: 'pct' });
+    });
+
+    it('handles decimal percentage strings like "62.5%"', () => {
+      const result = translator.encode({
+        nodes: [{ attributes: { 'w:w': '62.5%', 'w:type': 'pct' } }],
+      });
+      expect(result).toEqual({ value: 3125, type: 'pct' });
+    });
+
+    it('does not convert percentage string when type is not "pct"', () => {
+      const result = translator.encode({
+        nodes: [{ attributes: { 'w:w': '100%', 'w:type': 'dxa' } }],
+      });
+      // parseInt("100%") = 100, kept as-is for non-pct types
+      expect(result).toEqual({ value: 100, type: 'dxa' });
+    });
+
+    it('handles numeric fiftieths format (5000 = 100%) unchanged', () => {
+      const result = translator.encode({
+        nodes: [{ attributes: { 'w:w': '5000', 'w:type': 'pct' } }],
+      });
+      expect(result).toEqual({ value: 5000, type: 'pct' });
+    });
+
     it('returns undefined if w:w is missing', () => {
       const result = translator.encode({ nodes: [{ attributes: { 'w:type': 'dxa' } }] });
       expect(result).toBeUndefined();
diff --git a/packages/super-editor/src/core/super-converter/v3/handlers/w/tcW/tcW-translator.test.js b/packages/super-editor/src/core/super-converter/v3/handlers/w/tcW/tcW-translator.test.js
index 6dc14bdf9b..90757a8673 100644
--- a/packages/super-editor/src/core/super-converter/v3/handlers/w/tcW/tcW-translator.test.js
+++ b/packages/super-editor/src/core/super-converter/v3/handlers/w/tcW/tcW-translator.test.js
@@ -22,6 +22,21 @@ describe('w:tcW translator (tcW)', () => {
       const result = tcWTranslator.encode({ nodes: [{ attributes: { 'w:type': 'dxa' } }] });
       expect(result).toBeUndefined();
     });
+
+    // SD-1633: ECMA-376 percentage string handling for cell widths
+    it('converts percentage string "62%" with type="pct" to fiftieths (3100)', () => {
+      const result = tcWTranslator.encode({
+        nodes: [{ attributes: { 'w:w': '62%', 'w:type': 'pct' } }],
+      });
+      expect(result).toEqual({ value: 3100, type: 'pct' });
+    });
+
+    it('converts percentage string "8%" with type="pct" to fiftieths (400)', () => {
+      const result = tcWTranslator.encode({
+        nodes: [{ attributes: { 'w:w': '8%', 'w:type': 'pct' } }],
+      });
+      expect(result).toEqual({ value: 400, type: 'pct' });
+    });
   });
 
   describe('decode', () => {