diff --git a/apps/builder/app/shared/html.test.tsx b/apps/builder/app/shared/html.test.tsx
index 74b235aa2d1d..403b3f50a494 100644
--- a/apps/builder/app/shared/html.test.tsx
+++ b/apps/builder/app/shared/html.test.tsx
@@ -280,6 +280,27 @@ test("generate style attribute as local styles", () => {
   );
 });
 
+test("generate nested css math functions as unparsed local styles", () => {
+  const value =
+    "clamp(1rem, calc(1rem + (2rem - 1rem) * ((100vw - 20rem) / (80rem - 20rem))), 2rem)";
+  const fragment = generateFragmentFromHtml(`
+    <div style="font-size:${value}">One clamp div</div>
+  `);
+
+  expect(fragment.styles).toEqual(
+    expect.arrayContaining([
+      expect.objectContaining({
+        property: "fontSize",
+        value: {
+          type: "unparsed",
+          value:
+            "clamp(1rem,calc(1rem + (2rem - 1rem)*((100vw - 20rem)/(80rem - 20rem))),2rem)",
+        },
+      }),
+    ])
+  );
+});
+
 test("script as html embed", () => {
   expect(generateFragmentFromHtml(`<script>a;</script>`)).toEqual(
     renderTemplate(
diff --git a/packages/css-data/src/parse-css-value.test.ts b/packages/css-data/src/parse-css-value.test.ts
index 0252be04062c..3b875822b12f 100644
--- a/packages/css-data/src/parse-css-value.test.ts
+++ b/packages/css-data/src/parse-css-value.test.ts
@@ -73,11 +73,44 @@ describe("Parse CSS value", () => {
       });
     });
 
+    test("Nested CSS math values", () => {
+      const value =
+        "clamp(1rem, calc(1rem + (2rem - 1rem) * ((100vw - 20rem) / (80rem - 20rem))), 2rem)";
+
+      expect(parseCssValue("font-size", value)).toEqual({
+        type: "unparsed",
+        value,
+      });
+    });
+
+    test("CSS numeric functions", () => {
+      expect(parseCssValue("width", "round(10px, 1px)")).toEqual({
+        type: "unparsed",
+        value: "round(10px, 1px)",
+      });
+      expect(parseCssValue("width", "abs(-10px)")).toEqual({
+        type: "unparsed",
+        value: "abs(-10px)",
+      });
+      expect(parseCssValue("width", "calc(pi * 1px)")).toEqual({
+        type: "unparsed",
+        value: "calc(pi * 1px)",
+      });
+    });
+
     test("Invalid function values", () => {
       expect(parseCssValue("width", "blur(4)")).toEqual({
         type: "invalid",
         value: "blur(4)",
       });
+      expect(parseCssValue("font-size", "clamp(foo)")).toEqual({
+        type: "invalid",
+        value: "clamp(foo)",
+      });
+      expect(parseCssValue("color", "abs(-10px)")).toEqual({
+        type: "invalid",
+        value: "abs(-10px)",
+      });
     });
   });
 
diff --git a/packages/css-data/src/parse-css-value.ts b/packages/css-data/src/parse-css-value.ts
index 3d0a6ff07d60..86ffa8005832 100644
--- a/packages/css-data/src/parse-css-value.ts
+++ b/packages/css-data/src/parse-css-value.ts
@@ -1,5 +1,6 @@
 import {
   type CssNode,
+  definitionSyntax,
   type FunctionNode,
   generate,
   lexer,
@@ -54,6 +55,91 @@ const splitRepeated = (nodes: CssNode[]) => {
   return lists;
 };
 
+const cssNumericFunctionNames = new Set([
+  "calc",
+  "min",
+  "max",
+  "clamp",
+  "round",
+  "mod",
+  "rem",
+  "sin",
+  "cos",
+  "tan",
+  "asin",
+  "acos",
+  "atan",
+  "atan2",
+  "pow",
+  "sqrt",
+  "hypot",
+  "log",
+  "exp",
+  "abs",
+  "sign",
+]);
+
+const cssMathConstants = new Set(["e", "pi", "infinity", "-infinity", "nan"]);
+
+const cssNumericTypeNames = new Set([
+  "length",
+  "length-percentage",
+  "percentage",
+  "number",
+  "integer",
+  "angle",
+  "time",
+  "frequency",
+  "resolution",
+  "flex",
+  "alpha-value",
+]);
+
+const canFallbackToCssMath = (ast: CssNode, syntax: string | undefined) => {
+  if (syntax === undefined) {
+    return false;
+  }
+
+  let hasCssNumericType = false;
+  try {
+    definitionSyntax.walk(definitionSyntax.parse(syntax), (node) => {
+      if (
+        node.type === "Type" &&
+        "name" in node &&
+        cssNumericTypeNames.has(node.name)
+      ) {
+        hasCssNumericType = true;
+      }
+    });
+  } catch {
+    return false;
+  }
+  if (hasCssNumericType === false) {
+    return false;
+  }
+
+  let hasCssNumericFunction = false;
+  let hasUnknownIdentifier = false;
+  walk(ast, (node) => {
+    if (node.type === "Function" && cssNumericFunctionNames.has(node.name)) {
+      hasCssNumericFunction = true;
+    }
+    if (
+      node.type === "Identifier" &&
+      cssMathConstants.has(node.name.toLowerCase()) === false
+    ) {
+      hasUnknownIdentifier = true;
+    }
+  });
+  return hasCssNumericFunction && hasUnknownIdentifier === false;
+};
+
+const getSyntaxMatchErrorSyntax = (error: Error | null | undefined) => {
+  if (error != null && "syntax" in error && typeof error.syntax === "string") {
+    return error.syntax;
+  }
+};
+
 // Because csstree parser has bugs we use CSSStyleValue to validate css properties if available
 // and fall back to csstree.
 export const isValidDeclaration = (
@@ -109,6 +195,10 @@ export const isValidDeclaration = (
   // @todo remove after csstree fixes
   // - https://github.com/csstree/csstree/issues/246
   // - https://github.com/csstree/csstree/issues/164
+  if (typeof CSS !== "undefined" && CSS.supports(property, value)) {
+    return true;
+  }
+
   if (typeof CSSStyleValue !== "undefined") {
     try {
       CSSStyleValue.parse(property, value);
@@ -143,6 +233,17 @@ export const isValidDeclaration = (
     return true;
   }
 
+  // css-tree does not fully validate modern CSS math with nested calc()
+  // operators, for example `font-size: clamp(... calc(... / ...) ...)`.
+  // Browser-valid values should be preserved as unparsed instead of stored as
+  // invalid values, which are intended for transient editor state.
+  if (
+    matchResult.matched == null &&
+    canFallbackToCssMath(ast, getSyntaxMatchErrorSyntax(matchResult.error))
+  ) {
+    return true;
+  }
+
   return matchResult.matched != null;
 };