Pull Request Size measures the number of lines changed within each pull request submitted for review.

Reviewing pull requests can be one of the most time consuming activities of a team’s software development process.

Making smaller pull requests is the best way to speed up time spent reviewing your peer’s work. By applying the discipline to break down pull requests into smaller, manageable batches of code, it’s much quicker for reviewers to understand the context, reason with the logic and detect defects that need remediation.

Small pull requests also make it more likely for code to be thoroughly reviewed before approval. It helps to speed up the review, reduces risk of introducing bugs into the codebase, helps not to block other developers and speeds up the process to finalise and ship the team’s product to customers for feedback.

Large pull requests tend to be glazed over and rubber stamped, limiting the effectiveness of defect detection.

Common practice suggest developers should review Pull Requests no more than 200-400 lines of code (LOC) at a time. This is because the brain can only process so much information at a time. Beyond 400 LOC, the ability to find defects diminishes.

Research also indicates that a review of 200-400 LOC over 60-90 minutes should yield a 70-90% defect discovery rate.

Umano measures Size of Pull Request through:

Each model looks at specific activities within the tools. Below is a list of activities that contribute to Pull Request Size and activities that do not have an impact on this metric.