diff --git a/lib/rules/function-calc-no-unspaced-operator/README.md b/lib/rules/function-calc-no-unspaced-operator/README.md
index 4801bdf33d..9f5ce7d8b3 100644
--- a/lib/rules/function-calc-no-unspaced-operator/README.md
+++ b/lib/rules/function-calc-no-unspaced-operator/README.md
@@ -11,6 +11,8 @@ a { top: calc(1px + 2px); }
 
 Before the operator, there must be a single whitespace or a newline plus indentation. After the operator, there must be a single whitespace or a newline.
 
+Note: The `*` and `/` operators do not require whitespace (but it is usually recommened for consistency).
+
 The [`fix` option](../../../docs/user-guide/usage/options.md#fix) can automatically fix all of the problems reported by this rule.
 
 ## Options
@@ -41,6 +43,11 @@ a { top: calc(1px + 2px); }
 a { top: calc(calc(1em * 2) / 3); }
 ```
 
+<!-- prettier-ignore -->
+```css
+a { top: calc(calc(1em*2)/3); }
+```
+
 <!-- prettier-ignore -->
 ```css
 a {
diff --git a/lib/rules/function-calc-no-unspaced-operator/__tests__/index.js b/lib/rules/function-calc-no-unspaced-operator/__tests__/index.js
index 09b588ea1f..f4bc6f9ebf 100644
--- a/lib/rules/function-calc-no-unspaced-operator/__tests__/index.js
+++ b/lib/rules/function-calc-no-unspaced-operator/__tests__/index.js
@@ -32,9 +32,27 @@ testRule({
 		{
 			code: 'a { top: calc(1px * 2); }',
 		},
+		{
+			code: 'a { top: calc(1px*2); }',
+		},
+		{
+			code: 'a { top: calc(1px *2); }',
+		},
+		{
+			code: 'a { top: calc(1px* 2); }',
+		},
 		{
 			code: 'a { top: calc(1px / 2); }',
 		},
+		{
+			code: 'a { top: calc(1px/2); }',
+		},
+		{
+			code: 'a { top: calc(1px /2); }',
+		},
+		{
+			code: 'a { top: calc(1px/ 2); }',
+		},
 		{
 			code: 'a { top: calc(1px * -0.2); }',
 		},
@@ -153,6 +171,36 @@ testRule({
 			code: 'margin-top: calc(var(--some-variable)\r\n\t+ var(--some-other-variable));',
 			description: 'CRLF newline and tab before operator',
 		},
+		{
+			code: 'a { padding: 10px calc(calc(1px + 2px)* 3px); }',
+		},
+		{
+			code: 'a { padding: 10px calc(calc(1px* 2px) + 3px); }',
+		},
+		{
+			code: 'a { padding: 10px calc(1px /2); }',
+		},
+		{
+			code: 'a { padding: 10px calc(1px/ 2); }',
+		},
+		{
+			code: 'a { padding: 10px calc(1px *2); }',
+		},
+		{
+			code: 'a { padding: 10px calc(1px* 2); }',
+		},
+		{
+			code: 'a { top: calc(calc(1px + 2px)* 3px); }',
+		},
+		{
+			code: 'a { top: calc(calc(1px* 2px) + 3px); }',
+		},
+		{
+			code: 'a { top: calc(10px*var(--foo)); }',
+		},
+		{
+			code: 'a { top: calc(10px/var(--foo)); }',
+		},
 	],
 
 	reject: [
@@ -257,60 +305,6 @@ testRule({
 			endLine: 1,
 			endColumn: 19,
 		},
-		{
-			code: 'a { top: calc(1px* 2); }',
-			fixed: 'a { top: calc(1px * 2); }',
-			message: messages.expectedBefore('*'),
-			line: 1,
-			column: 18,
-			endLine: 1,
-			endColumn: 19,
-		},
-		{
-			code: 'a { top: calc(1px *2); }',
-			fixed: 'a { top: calc(1px * 2); }',
-			message: messages.expectedAfter('*'),
-			line: 1,
-			column: 19,
-			endLine: 1,
-			endColumn: 20,
-		},
-		{
-			code: 'a { top: calc(1px/ 2); }',
-			fixed: 'a { top: calc(1px / 2); }',
-			message: messages.expectedBefore('/'),
-			line: 1,
-			column: 18,
-			endLine: 1,
-			endColumn: 19,
-		},
-		{
-			code: 'a { top: calc(1px /2); }',
-			fixed: 'a { top: calc(1px / 2); }',
-			message: messages.expectedAfter('/'),
-			line: 1,
-			column: 19,
-			endLine: 1,
-			endColumn: 20,
-		},
-		{
-			code: 'a { top: calc(calc(1px* 2px) + 3px); }',
-			fixed: 'a { top: calc(calc(1px * 2px) + 3px); }',
-			message: messages.expectedBefore('*'),
-			line: 1,
-			column: 23,
-			endLine: 1,
-			endColumn: 24,
-		},
-		{
-			code: 'a { top: calc(calc(1px + 2px)* 3px); }',
-			fixed: 'a { top: calc(calc(1px + 2px) * 3px); }',
-			message: messages.expectedBefore('*'),
-			line: 1,
-			column: 30,
-			endLine: 1,
-			endColumn: 31,
-		},
 		{
 			code: 'a { top: calc(1px +2px); }',
 			fixed: 'a { top: calc(1px + 2px); }',
@@ -403,60 +397,6 @@ testRule({
 			endLine: 1,
 			endColumn: 28,
 		},
-		{
-			code: 'a { padding: 10px calc(1px* 2); }',
-			fixed: 'a { padding: 10px calc(1px * 2); }',
-			message: messages.expectedBefore('*'),
-			line: 1,
-			column: 27,
-			endLine: 1,
-			endColumn: 28,
-		},
-		{
-			code: 'a { padding: 10px calc(1px *2); }',
-			fixed: 'a { padding: 10px calc(1px * 2); }',
-			message: messages.expectedAfter('*'),
-			line: 1,
-			column: 28,
-			endLine: 1,
-			endColumn: 29,
-		},
-		{
-			code: 'a { padding: 10px calc(1px/ 2); }',
-			fixed: 'a { padding: 10px calc(1px / 2); }',
-			message: messages.expectedBefore('/'),
-			line: 1,
-			column: 27,
-			endLine: 1,
-			endColumn: 28,
-		},
-		{
-			code: 'a { padding: 10px calc(1px /2); }',
-			fixed: 'a { padding: 10px calc(1px / 2); }',
-			message: messages.expectedAfter('/'),
-			line: 1,
-			column: 28,
-			endLine: 1,
-			endColumn: 29,
-		},
-		{
-			code: 'a { padding: 10px calc(calc(1px* 2px) + 3px); }',
-			fixed: 'a { padding: 10px calc(calc(1px * 2px) + 3px); }',
-			message: messages.expectedBefore('*'),
-			line: 1,
-			column: 32,
-			endLine: 1,
-			endColumn: 33,
-		},
-		{
-			code: 'a { padding: 10px calc(calc(1px + 2px)* 3px); }',
-			fixed: 'a { padding: 10px calc(calc(1px + 2px) * 3px); }',
-			message: messages.expectedBefore('*'),
-			line: 1,
-			column: 39,
-			endLine: 1,
-			endColumn: 40,
-		},
 		{
 			code: 'a { padding: 10px calc(1px +2px); }',
 			fixed: 'a { padding: 10px calc(1px + 2px); }',
@@ -564,6 +504,33 @@ testRule({
 	customSyntax: 'postcss-scss',
 	fix: true,
 
+	accept: [
+		{
+			code: 'a { top: calc(100%*#{$foo}); }',
+		},
+		{
+			code: 'a { top: calc(100% *#{$foo}); }',
+		},
+		{
+			code: 'a { top: calc(100%* #{$foo}); }',
+		},
+		{
+			code: 'a { top: calc(100% * #{$foo}); }',
+		},
+		{
+			code: 'a { top: calc(100%/#{$foo}); }',
+		},
+		{
+			code: 'a { top: calc(100% /#{$foo}); }',
+		},
+		{
+			code: 'a { top: calc(100%/ #{$foo}); }',
+		},
+		{
+			code: 'a { top: calc(100% / #{$foo}); }',
+		},
+	],
+
 	reject: [
 		{
 			code: 'a { top: calc(100%- #{$foo}); }',
@@ -574,15 +541,6 @@ testRule({
 			endLine: 1,
 			endColumn: 20,
 		},
-		{
-			code: 'a { top: calc(100% *#{$foo}); }',
-			fixed: 'a { top: calc(100% * #{$foo}); }',
-			message: messages.expectedAfter('*'),
-			line: 1,
-			column: 20,
-			endLine: 1,
-			endColumn: 21,
-		},
 		{
 			code: 'a { top: calc(100% -#{$foo}); }',
 			fixed: 'a { top: calc(100% - #{$foo}); }',
diff --git a/lib/rules/function-calc-no-unspaced-operator/index.js b/lib/rules/function-calc-no-unspaced-operator/index.js
index 1d26096e50..7d9a3cbfb5 100644
--- a/lib/rules/function-calc-no-unspaced-operator/index.js
+++ b/lib/rules/function-calc-no-unspaced-operator/index.js
@@ -22,8 +22,9 @@ const meta = {
 	url: 'https://stylelint.io/user-guide/rules/list/function-calc-no-unspaced-operator',
 };
 
-const OPERATORS = new Set(['*', '/', '+', '-']);
-const OPERATOR_REGEX = /[*/+-]/;
+const OPERATORS = new Set(['+', '-']);
+const OPERATOR_REGEX = /[+-]/;
+const ALL_OPERATORS = new Set([...OPERATORS, '*', '/']);
 
 /** @type {import('stylelint').Rule} */
 const rule = (primary, _secondaryOptions, context) => {
@@ -173,8 +174,10 @@ const rule = (primary, _secondaryOptions, context) => {
 				const firstNode = nodes[0];
 
 				assert(firstNode);
-				const operatorIndex =
-					(firstNode.type === 'word' || -1) && firstNode.value.search(OPERATOR_REGEX);
+
+				if (firstNode.type !== 'word') return false;
+
+				const operatorIndex = firstNode.value.search(OPERATOR_REGEX);
 				const operator = firstNode.value.slice(operatorIndex, operatorIndex + 1);
 
 				if (operatorIndex <= 0) return false;
@@ -239,10 +242,22 @@ const rule = (primary, _secondaryOptions, context) => {
 				const lastNode = nodes[nodes.length - 1];
 
 				assert(lastNode);
-				const operatorIndex =
-					(lastNode.type === 'word' || -1) && lastNode.value.search(OPERATOR_REGEX);
 
-				if (lastNode.value[operatorIndex - 1] === ' ') return false;
+				if (lastNode.type !== 'word') return false;
+
+				const operatorIndex = lastNode.value.search(OPERATOR_REGEX);
+
+				if (operatorIndex === -1) return false;
+
+				if (lastNode.value.charAt(operatorIndex - 1) === ' ') return false;
+
+				// E.g. "10px * -2" when the last node is "-2"
+				if (
+					isOperator(nodes[nodes.length - 3], ALL_OPERATORS) &&
+					isSingleSpace(nodes[nodes.length - 2])
+				) {
+					return false;
+				}
 
 				if (context.fix) {
 					needsFix = true;
@@ -252,9 +267,8 @@ const rule = (primary, _secondaryOptions, context) => {
 					return true;
 				}
 
-				const operator = lastNode.value[operatorIndex];
+				const operator = lastNode.value.charAt(operatorIndex);
 
-				assert(operator);
 				complain(
 					messages.expectedOperatorBeforeSign(operator),
 					decl,
@@ -308,7 +322,7 @@ const rule = (primary, _secondaryOptions, context) => {
 				let foundOperatorNode = false;
 
 				for (const [nodeIndex, currNode] of node.nodes.entries()) {
-					if (currNode.type !== 'word' || !OPERATORS.has(currNode.value)) continue;
+					if (!isOperator(currNode)) continue;
 
 					foundOperatorNode = true;
 
@@ -351,6 +365,15 @@ function isSingleSpace(node) {
 	return node != null && node.type === 'space' && node.value === ' ';
 }
 
+/**
+ * @param {import('postcss-value-parser').Node | undefined} node
+ * @param {Set<string>} [operators]
+ * @returns {node is import('postcss-value-parser').WordNode}
+ */
+function isOperator(node, operators = OPERATORS) {
+	return node != null && node.type === 'word' && operators.has(node.value);
+}
+
 rule.ruleName = ruleName;
 rule.messages = messages;
 rule.meta = meta;