diff --git a/.changeset/wet-countries-think.md b/.changeset/wet-countries-think.md
new file mode 100644
index 0000000000..7dd9a539de
--- /dev/null
+++ b/.changeset/wet-countries-think.md
@@ -0,0 +1,5 @@
+---
+"stylelint": patch
+---
+
+Fixed: `function-calc-no-unspaced-operator` performance
diff --git a/lib/rules/function-calc-no-unspaced-operator/index.js b/lib/rules/function-calc-no-unspaced-operator/index.js
index 57f42f2603..0e7c00f07e 100644
--- a/lib/rules/function-calc-no-unspaced-operator/index.js
+++ b/lib/rules/function-calc-no-unspaced-operator/index.js
@@ -48,9 +48,13 @@ const rule = (primary, _secondaryOptions, context) => {
 		}
 
 		root.walkDecls((decl) => {
+			const value = getDeclarationValue(decl);
+
+			if (!OPERATOR_REGEX.test(value)) return;
+
 			let needsFix = false;
 			const valueIndex = declarationValueIndex(decl);
-			const parsedValue = valueParser(getDeclarationValue(decl));
+			const parsedValue = valueParser(value);
 
 			/**
 			 * @param {import('postcss-value-parser').Node} operatorNode