Contributor Activity Calculator

Measure contributor activity levels from commits, PRs and reviews over time.

About Contributor Activity Calculator

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

Worked example

With the default values below, Contributor Activity Calculator returns Active Contributor Ratio of 16.5%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Total Contributors (All-Time)accepts 0–1,000,000 people: 85 people
Contributors Active in Periodaccepts 0–1,000,000 people: 14 people
Core Contributors (>10 Commits)accepts 0–1,000,000 people: 5 people

Results

Active Contributor Ratio: 16.5%
Bus Factor Risk: Moderate
Core Share of Active Contributors: 35.7%

Step by step

1Active ratio: active / total= 16.5%
2Core share of active= 35.7%

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or fees or charges into account.
Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

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.