Total PR Cycle Time (Average)

Last updated: January 7, 2026

Definition

PR Cycle Time measures the total time from when the first commit is created until the PR is merged.

Metric Name

pr_cycle_time

Start Event

FirstCommit — when the first commit is created on the branch

End Event

Merged — when the PR is merged into the target branch

Formula

Merged Timestamp - FirstCommit Timestamp

How "Average" is Computed

Span uses a trimmed mean approach, not a simple arithmetic average:

  1. Outlier Capping: Each individual PR cycle time is capped at 30 days (2,592,000 seconds)

    • If a PR takes 45 days, it's treated as 30 days for the average calculation

    • Implemented via: MIN(actual_cycle_time, 30_days)

  2. Aggregation: After capping, the standard AVG() function is applied

Calculation Logic:

FOR each merged PR:
  capped_cycle_time = MIN(actual_cycle_time, 30 days)

Average PR Cycle Time = SUM(all_capped_cycle_times) / COUNT(PRs)

What's Included

The metric only counts PRs that meet these criteria:

  • ✅ Status = Merged

  • ✅ Created by developers (flagged as is_dev_contributor)

  • ✅ Cycle time > 0 (valid timestamps)

  • ❌ Excludes bot-created PRs

  • ❌ Excludes non-contributor activity

Other Aggregation Options

When viewing PR Cycle Time in Span, you can choose different aggregations:

AggregationDescription

Average (default)

Trimmed mean capped at 30 days

P50

Median — 50% of PRs are faster

P75

75th percentile — 75% of PRs are faster

P90

90th percentile — 90% of PRs are faster

Max

Longest PR cycle time in the dataset

Why Trimmed Averaging?

The 30-day cap prevents extremely long-running PRs (like long-lived feature branches or stale PRs) from artificially inflating the average. This keeps the metric representative of your team's typical workflow.

Example:

  • Team has 10 PRs: nine take 2 hours each, one takes 60 days

  • Without trimming: Average = ~144 hours (misleading)

  • With 30-day cap: Average = ~2.6 hours (more representative)

Complete PR Lifecycle Breakdown

PR Cycle Time (FirstCommit → Merged) encompasses all these stages:

  1. Coding (FirstCommit → PR Opened)

  2. Awaiting First Review (PR Opened → FirstReview)

  3. Reworking (FirstReview → LastAction)

  4. Idling (LastAction → Merged)

Total PR Cycle Time = Coding + Awaiting First Review + Reworking + Idling

For more details on the PR Lifecycle stages, see here.