Lines of Code (LOC) as a Metric

Also Known As

TL;DR

Explanation

Lines of Code has three variants: physical LOC (all lines), source LOC (non-blank, non-comment), and logical LOC (statements). LOC is useful for normalising defect density (defects per KLOC) and tracking codebase growth trends. As a standalone quality metric it is misleading — a 500-line function and ten 50-line functions share the same LOC but differ enormously in maintainability. LOC is best used alongside complexity metrics (cyclomatic, cognitive) rather than as a target. Setting LOC limits per file in CI is a lightweight smell detector that flags candidates for refactoring review.

Common Misconception

Why It Matters

Common Mistakes

• Treating LoC as a productivity metric — incentivising more lines produces bloated, verbose code.
• Using LoC as the only size metric — a 50-line function with 15 branches is more problematic than a 200-line class with simple sequential logic.
• Reducing LoC by compressing multiple statements onto one line — not an improvement.
• Not normalising LoC by language — PHP and Java will naturally produce different counts for equivalent logic.

Code Examples

// 'Reducing' LoC by unreadable compression — worse, not better:
function p($u){return$u->a&&$u->v&&!$u->b?'active':($u->b?'banned':'inactive');}
// Low line count, zero readability — meaningful LoC reduction requires refactoring, not compression

// Lines of Code (LOC) is a simple but blunt metric
// Logical LOC (non-blank, non-comment) is more meaningful

// Tools to measure PHP LOC:
$ phploc src/
// Reports: LOC, LLOC (logical), CLOC (comment), NCLOC, methods, classes

// Rough guidelines (not strict rules):
// Method: < 20 LLOC
// Class:  < 200 LLOC
// File:   < 400 LLOC

// LOC alone doesn't indicate quality — pair with:
// - Cyclomatic complexity
// - Test coverage
// - Maintainability Index

// SonarQube and PHPMetrics produce LOC dashboards:
$ phpmetrics --report-html=report/ src/

References

• ↗ https://en.wikipedia.org/wiki/Source_lines_of_code

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