Guessing Review Time Is How Deadlines Slip
When someone asks you to "take a look" at a PR, not knowing how long it will actually take makes it hard to prioritize. Code review research from organizations like Google and SmartBear suggests reviewers can only maintain defect-catching quality at roughly 200-400 lines per hour — go faster than that and quality drops off fast.
This calculator starts from an industry-average baseline of 300 lines per hour, then factors in your added and deleted lines along with a complexity level (Low, Medium, High). A one-line typo fix and a core logic rewrite take very different amounts of time even at the same line count, so the multiplier adjusts the estimate closer to reality.
If the estimate comes out too long, consider splitting the PR into smaller pieces. Multiple studies point to a sharp drop in defect detection once a PR crosses roughly 400 lines, so reviewing smaller changes more often tends to raise a team's overall code quality.
Frequently Asked Questions
It is based on roughly 300 lines per hour, a rate suggested by multiple code review studies, then adjusted by the complexity multiplier you select.
Pick Low for simple text or config changes, Medium for typical features or bug fixes, and High for architecture changes or core logic edits.
Studies show defect detection rates drop sharply once a PR exceeds about 400 lines, so splitting large PRs into smaller ones is usually the better move.