Cyclomatic Complexity Calculator

Cyclomatic complexity (CC) measures the number of linearly independent paths through a function's source code. It equals 1 plus the number of decision points: each if, else if, for, while, do, case, catch, &&, ||, and ternary (?) adds 1. A CC of 1–5 is simple; 6–10 is moderate; 11–20 is high and should be refactored; 21+ is unmaintainable.

McCabe's original guideline: CC ≤ 10 per function is the widely-accepted safe threshold. Many teams use 15 as a practical ceiling. Functions above 20 are considered too risky to modify safely without comprehensive test coverage. The key insight: CC also equals the minimum number of test cases needed to cover all branches.

This tool counts: if / else if, for / for-of / for-in, while / do-while, switch case / default, catch blocks, logical && and ||, ternary ? operator, and optional chaining ?. (optional chaining). Each adds one independent path through the code.

Extract complex conditions into named boolean variables. Use early returns (guard clauses) to flatten nested ifs. Split long functions into smaller single-responsibility helpers. Replace if/else chains with lookup tables or strategy patterns. Use Array methods (filter, map, reduce) instead of manual loops with conditions.

No. Cyclomatic complexity counts structural paths (good for test coverage planning). Cognitive complexity (SonarSource) counts how hard code is to understand — it adds extra weight for nesting depth. A simple flat switch with 10 cases is CC=10 but low cognitive complexity. A deeply nested if-else tree may be CC=5 but high cognitive complexity. Both metrics are useful.