Code review usefulness measures whether reviews find potential problems, improve quality, and support feedback without turning approval speed into the goal. Approval rates and review time can create harmful shortcuts when teams optimize for favorable numbers. section 9.2.5 section 9.3
Treat review metrics as signals, then interpret them through team context:
- Code churn shows how much code is changed, reworked, or reverted after review. section 9.2.5
- Review time can indicate timely feedback and manageable pull requests, but slower cycles may reveal bottlenecks or unclear requirements. section 9.2.5
- Review participation and pull request size add context that approval rates alone cannot provide. section 9.3
Table 9.1 Code review metrics
|
Metric
|
What does it measure?
|
How to measure it
|
Effect
|
|---|---|---|---|
|
Code churn
|
How often a given piece of code is changed/ reworked after a review
|
Track lines of code added, deleted, and reverted after a review.
|
High churn can suggest overly stringent reviews or submitted code that is subpar/unclear.
Low churn can indicate improved quality and legibility.
|
|
Review time
|
How long an average code review lasts
|
Track the time between opening a PR and merging it.
|
Faster review cycles can indicate timely feedback, greater alignment between author and reviewer, and manageable PR sizes.
Slower review cycles can indicate communication bottlenecks, larger PR sizes, and a lack of clarity in requirements.
|
|
Review participation
|
How active team members are in code reviews
|
Track the number of reviews participated in, comments left, and average review time per developer.
|
High rates suggest a more collaborative culture and thorough individual reviews.
Low rates can suggest uneven PR workload distribution, communication and feedback difficulties, or less engagement in reviews overall.
|
|
PR size
|
The average size of a pull request
|
Track the number of files/lines of code a PR has.
|
Larger sizes can indicate unclear work tickets or acceptance criteria.
Smaller sizes can suggest better planning and alignment on work tickets.
|
Use the code review metrics table to compare what each metric measures, how to track it, and what high or low values may suggest. section 9.2.5
