Contributor Activity Calculator

Calculate the share of contributors actively committing in a period versus the full historical contributor base.

Inputs

Total Contributors (All-Time)people

Unique authors who have ever committed to the repository.

Contributors Active in Periodpeople

Unique authors with at least one commit in the analyzed period.

Core Contributors (>10 Commits)people

Contributors with more than 10 commits in the period — a proxy for sustained engagement.

Active Contributor Ratio

16.5%

Bus Factor Risk

Moderate

Core Share of Active Contributors

35.7%

Step by step

Active ratio: active / total
14 / 85
= 16.5%
Core share of active
5 / 14
= 35.7%

How it works

Active contributor ratio measures how much of a project's historical contributor base is still engaged. Formula: active_ratio = contributors_with_commits_in_period / total_contributors. Pairing this with the count of 'core' contributors (a common threshold is >10 commits in the period) surfaces bus-factor risk — how much the project depends on a small handful of people.

Formula

active_ratio_percent = (active_contributors / total_contributors) × 100

active_contributors: Contributors with commits in the period
total_contributors: All-time unique contributors

Frequently Asked Questions

What's a healthy active contributor ratio?

For long-lived open source projects, 10-25% active-in-period is common and healthy since most historical contributors made one-off fixes. For internal product teams, you'd expect this closer to 80-100% since most contributors are current employees.

What is 'bus factor' and why does it matter?

Bus factor is the minimum number of people who could leave before a project stalls. A low core-contributor count (1-2 people) means critical knowledge is concentrated and creates high organizational risk.

How do I compute this from Git history?

Use `git shortlog -sn --since=<date>` for the active list and `git shortlog -sn` (no date filter) for all-time contributors, then compare unique author counts.

Does one-time contributors count against project health?

Not necessarily — a healthy funnel of new one-time contributors (e.g. drive-by PRs) is a good sign for open source growth, even if the active ratio looks low, as long as core maintainers remain stable.

You might also need

Commit Frequency Calculator Git Repository Health Score Calculator Commit Velocity Calculator