PR Size Analyzer
Analyze your pull request sizes and get recommendations. Learn the optimal PR size for faster reviews and fewer bugs.
PR size is the number of lines and files a pull request changes, and it is one of the strongest predictors of how a review goes. Big PRs sit in the queue longer, get skimmed instead of read, and ship more bugs. Small ones get real attention and merge fast.
This tool is for engineers and team leads who want a quick read on a change before they ask for review. Enter the lines changed (and optionally files and your team's typical review time) and it returns a size category, a risk level, an estimated review time, and a first-pass approval likelihood, plus concrete advice on whether to split the work.
Enter PR Details
If provided, we'll calibrate the review time estimate to your team's pace.
Enter the lines of code changed to analyze your PR size.
Research Behind This Tool
This tool is based on extensive research from leading technology companies on the relationship between PR size and code quality.
Google Research
PRs under 200 lines have a 15% higher approval rate on first review. Smaller changes lead to faster iteration cycles.
Microsoft Research
PRs over 400 lines take 2x longer to review. Review quality drops significantly after 60-90 minutes of continuous review.
Industry Studies
Larger PRs have higher defect rates. Each additional 100 lines increases the probability of introducing a bug by approximately 15%.
PR Size Best Practices
Aim for 100-200 lines per PR
Keep under 5-10 files when possible
One logical change per PR
By feature, layer, or refactor vs. feature
How it’s calculated
The analyzer buckets a PR by total lines changed, raises the risk level when the file count or line count climbs, and estimates how long review will take based on how reviewer attention falls off as a change grows.
Size categories
- XS: under 10 lines. Trivial changes.
- S: 10 to 100 lines. The sweet spot for a thorough review.
- M: 100 to 400 lines. Reviewable, but needs focused time.
- L: 400 to 1,000 lines. Large enough that splitting usually pays off.
- XL: over 1,000 lines. Too big to review well in one sitting.
Risk level
Risk rises on either axis. More than 1,000 lines or 20 files reads as critical; more than 400 lines or 10 files as high; more than 100 lines or 5 files as medium. When you leave files blank the tool estimates one file per 50 lines so the risk read still holds.
Review time and approval rate
Estimated review time scales non-linearly: roughly 2 minutes per 10 lines under 100 lines, then slower per line as the change grows, because attention drops after about an hour at the desk. If you enter your team's average review time the estimate is calibrated against a 200-line baseline. The first-pass approval likelihood drops as size grows, reflecting the higher approval rates small PRs see.
Where the numbers come from
Pull lines changed and file count straight from the PR (additions plus deletions). Your average review time, if you have it, comes from your own cycle-time data or a tool that tracks time to first review.
Worked example
A developer opens a PR that changes 620 lines across 14 files and asks the tool to read it.
- 620 lines lands in the L band, so the change is flagged as large.
- Over 400 lines and over 10 files both push the risk level to high.
- Estimated review time comes to roughly 87 minutes once the file-count factor is applied, past the point where attention starts to fade.
- First-pass approval likelihood sits in the low-70s percent rather than the 90s a small PR would see.
The read: this PR is reviewable but the reviewer will run out of focus before the end, and the bottom of the diff gets a rubber stamp. Splitting it along a clean boundary - say the data layer in one PR and the UI in another - turns one tiring review into two quick ones, each with a much better chance of catching a real bug.
PR Size Benchmarks
| Metric | Elite | High | Medium | Low |
|---|---|---|---|---|
| Lines changed | Under 100 | 100-200 | 200-400 | Over 400 |
| Files changed | 1-3 | 3-5 | 5-10 | Over 10 |
| Review time | Under 20 min | 20-40 min | 40-60 min | Over 60 min |
| First-pass approval | 95%+ | 85-95% | 75-85% | Under 75% |
Source: Google and Microsoft code review research; CodePulse analysis of 3.4M PRs · Thresholds reflect where review quality and approval rates hold up versus fall off.
Our Take
The optimal PR size isn't about lines of code - it's about cognitive load.
A 50-line PR that changes 10 files is harder to review than a 200-line PR in one file. The real metric is how much mental effort a reviewer needs to hold context. This tool helps you find the sweet spot where changes are meaningful but still reviewable in a single focused session.
"PRs over 400 lines are 83% more likely to ship without meaningful review."
— CodePulse research on 803,000 PRs
Key terms
- Lines Changed
- Additions plus deletions in a pull request. The single number this tool uses to bucket size, since it tracks reviewer effort better than net line count.
- Files Changed
- How many distinct files the PR touches. A change spread across many files raises review difficulty even when the line count is modest, because the reviewer has to hold more context at once.
- Size Category
- The XS through XL band a PR falls into by lines changed. It is a shorthand for how reviewable the change is in one sitting.
- First-Pass Approval Rate
- The share of PRs approved on the first review without a round of requested changes. It tends to fall as PR size grows.
- Rubber-Stamp Approval
- An approval given without a careful read, common on large PRs once a reviewer tires. The change merges, but real review never happened.
Frequently Asked Questions
The optimal PR size is between 100-200 lines of code. Research from Google shows PRs under 200 lines have 15% higher first-pass approval rates, while Microsoft studies confirm PRs over 400 lines take twice as long to review. Aim for changes that can be reviewed in under 30 minutes to maintain review quality.
Want to track this automatically?
CodePulse connects to your GitHub and calculates these metrics in real-time. No more manual data entry or spreadsheets.
Free tier available. No credit card required.
See These Features in Action
Flag large PRs, single-owner changes, and untested modifications.
Break down cycle time into coding, waiting, review, and merge phases.
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