diff --git a/codesnap/utils/complexity.py b/codesnap/utils/complexity.py
new file mode 100644
index 0000000..077d962
--- /dev/null
+++ b/codesnap/utils/complexity.py
@@ -0,0 +1,173 @@
+"""Complexity calculation module for CodeSnap."""
+
+from pathlib import Path
+from typing import Optional
+
+
+class ComplexityCalculator:
+    """Calculates cyclomatic complexity for source code."""
+
+    def __init__(
+        self, low_threshold: int = 10, medium_threshold: int = 20, high_threshold: int = 50
+    ) -> None:
+        self.low_threshold = low_threshold
+        self.medium_threshold = medium_threshold
+        self.high_threshold = high_threshold
+
+    def calculate(self, content: str, language: str = "python") -> int:
+        """Calculate cyclomatic complexity for a file."""
+        complexity = 1
+
+        branching_keywords = self._get_branching_keywords(language)
+        for keyword in branching_keywords:
+            complexity += content.count(keyword)
+
+        lines = content.split("\n")
+        max_nesting = self._calculate_max_nesting(lines, language)
+        complexity += max_nesting // 2
+
+        long_functions = self._count_long_functions(lines, language)
+        complexity += long_functions
+
+        return complexity
+
+    def _get_branching_keywords(self, language: str) -> list[str]:
+        """Get branching keywords for a language."""
+        common_keywords = ["if ", "elif ", "else:", "for ", "while ", "except:", "finally:"]
+        language_keywords = {
+            "python": common_keywords + ["case ", "match "],
+            "javascript": common_keywords
+            + [
+                "switch (",
+                "case ",
+                "try {",
+                "catch (",
+                "&&",
+                "||",
+                "??",
+            ],
+            "typescript": common_keywords
+            + [
+                "switch (",
+                "case ",
+                "try {",
+                "catch (",
+                "&&",
+                "||",
+                "??",
+            ],
+            "go": ["if ", "else {", "for ", "switch ", "case ", "default:"],
+            "rust": ["if ", "else", "match ", "loop ", "while ", "match "],
+        }
+        return language_keywords.get(language, common_keywords)
+
+    def _calculate_max_nesting(self, lines: list[str], language: str) -> int:
+        """Calculate maximum nesting depth in the code."""
+        max_nesting = 0
+        current_nesting = 0
+
+        indent_char = "\t" if language in ("python", "yaml") else " "
+        for line in lines:
+            stripped = line.strip()
+            if not stripped or stripped.startswith("#") or stripped.startswith("//"):
+                continue
+
+            indent = len(line) - len(line.lstrip(indent_char))
+            new_nesting = indent // (4 if indent_char == " " else 1)
+
+            if new_nesting > current_nesting:
+                current_nesting = new_nesting
+                max_nesting = max(max_nesting, current_nesting)
+
+        return max_nesting
+
+    def _count_long_functions(self, lines: list[str], language: str) -> int:
+        """Count functions that exceed length threshold."""
+        threshold = 50
+        count = 0
+        in_function = False
+        func_start = 0
+
+        for i, line in enumerate(lines):
+            if language == "python":
+                if line.strip().startswith("def "):
+                    if in_function:
+                        func_len = i - func_start
+                        if func_len > threshold:
+                            count += 1
+                    in_function = True
+                    func_start = i
+            elif language in ("javascript", "typescript"):
+                if "function" in line or "=>" in line:
+                    if in_function:
+                        func_len = i - func_start
+                        if func_len > threshold:
+                            count += 1
+                    in_function = True
+                    func_start = i
+
+        if in_function:
+            func_len = len(lines) - func_start
+            if func_len > threshold:
+                count += 1
+
+        return count
+
+    def get_rating(self, complexity: int) -> str:
+        """Get complexity rating string."""
+        if complexity <= self.low_threshold:
+            return "low"
+        elif complexity <= self.medium_threshold:
+            return "medium"
+        elif complexity <= self.high_threshold:
+            return "high"
+        else:
+            return "critical"
+
+    def calculate_file_complexity(
+        self, file_path: Path, content: Optional[str] = None
+    ) -> dict[str, any]:
+        """Calculate complexity for a single file."""
+        if content is None:
+            try:
+                content = file_path.read_text(encoding="utf-8")
+            except Exception:
+                return {
+                    "path": str(file_path),
+                    "complexity": 0,
+                    "rating": "unknown",
+                    "error": "Could not read file",
+                }
+
+        language = self._detect_language(file_path)
+        complexity = self.calculate(content, language)
+
+        return {
+            "path": str(file_path),
+            "complexity": complexity,
+            "rating": self.get_rating(complexity),
+            "language": language,
+        }
+
+    def _detect_language(self, file_path: Path) -> str:
+        """Detect language from file extension."""
+        suffix = file_path.suffix.lower()
+        language_map = {
+            ".py": "python",
+            ".js": "javascript",
+            ".ts": "typescript",
+            ".go": "go",
+            ".rs": "rust",
+            ".java": "java",
+        }
+        return language_map.get(suffix, "python")
+
+    def calculate_batch(
+        self, files: list[Path], contents: dict[str, str]
+    ) -> dict[str, dict[str, any]]:
+        """Calculate complexity for multiple files."""
+        results = {}
+        for file_path in files:
+            content = contents.get(str(file_path))
+            results[str(file_path)] = self.calculate_file_complexity(file_path, content)
+        return results