Calculate average time from PR open to approval across your review process.
Average PR review time is the sum of every PR's review latency divided by PR count. Formula: avg_time = sum(review_times) / PR_count. Splitting this into time-to-first-review versus author response time to comments pinpoints where delay actually accumulates — a slow-to-review team looks very different from a team with fast reviews but slow author follow-through.
avg_review_time = sum_of_review_times / PR_count
Most commonly, time-to-first-review is measured from PR creation (or 'ready for review') to the first reviewer comment or approval — it's the most visible latency to the author and the easiest to pull from GitHub/GitLab APIs.
High-performing teams target under 24 business hours, with many aiming for same-day (a few hours) first response, even if full approval takes longer across review rounds.
The GitHub REST/GraphQL API exposes PR `created_at` and review `submitted_at` timestamps; tools like GitHub Insights, or simple scripts against the API, can aggregate these into averages.
PR review time is typically right-skewed — a few stale PRs waiting weeks pull the average up dramatically. Track median and p90 alongside the average for a fuller picture.