Kanban Card Calculation Example

What is Kanban?

Kanban is a Japanese term meaning "signboard" or "billboard." In project management, it refers to a visual system for managing work with an emphasis on continuous delivery without overloading the team.

The core principles of Kanban include:

• Visualize workflow
• Limit work in progress (WIP)
• Manage flow
• Make policies explicit
• Implement feedback loops
• Improve collaboratively
• Evolve experimentally

Kanban boards typically consist of columns representing different stages of work and cards representing individual tasks or user stories.

Key Kanban Metrics

Effective Kanban implementation requires tracking several key metrics:

1. Cycle Time: Time from when work starts until it's completed
2. Lead Time: Time from when work is requested until it's completed
3. Throughput: Number of items completed in a given period
4. Work in Progress (WIP): Number of items currently being worked on
5. Cumulative Flow Diagram: Visual representation of work items over time

These metrics help teams identify inefficiencies, optimize workflow, and continuously improve their processes.

Calculation Methods

Cycle Time Calculation

Cycle time is calculated as the average time each task takes to move through the workflow. The formula is:

For example, if 10 tasks took a total of 500 hours to complete, the cycle time would be 50 hours.

Lead Time Calculation

Lead time measures the total time from when a request is made until it's completed. The formula is:

For instance, if a feature was requested on January 1 and completed on January 15, the lead time is 14 days.

Throughput Calculation

Throughput is calculated by counting the number of completed items in a given time period. The formula is:

If a team completes 20 tasks in a month, their monthly throughput is 20 tasks.

Work in Progress (WIP) Limit

WIP limits are set to prevent overloading the team. A common approach is to use the Little's Law:

For example, if cycle time is 5 days and throughput is 10 items per month, the WIP limit might be set to 50 items.

Example Calculation

Let's walk through a practical example of calculating Kanban metrics for a software development team.

Scenario

A development team has completed 15 user stories over the past month. The total time spent on these stories was 750 hours. The team started working on these stories on average 3 days before they were completed.

Calculations

1. Cycle Time:

   Cycle Time = 750 hours / 15 stories = 50 hours per story

2. Lead Time:

   Lead Time = Cycle Time + Average Queue Time = 50 hours + (3 days × 8 hours/day) = 74 hours

3. Throughput:

   Throughput = 15 stories / 1 month = 15 stories per month

4. WIP Limit:

   WIP Limit = Cycle Time × Throughput = 50 hours × 15 stories = 750 story-hours

Interpretation

Based on these calculations:

• The team averages 50 hours per story (about 6.25 days)
• From request to completion, stories take about 9.25 days on average
• The team completes 15 stories per month
• The WIP limit suggests the team should not have more than 750 story-hours of work in progress

Interpreting Results

Understanding Kanban metrics helps teams make data-driven decisions:

• Cycle Time: Identify bottlenecks in the workflow
• Lead Time: Measure customer satisfaction and delivery speed
• Throughput: Assess team productivity and capacity
• WIP Limits: Prevent overloading and improve focus

Regularly reviewing these metrics allows teams to continuously improve their processes and deliver better results.