What is Little's Law?

Little's Law states that the average number of items in a stable system (WIP) equals the average arrival rate (Throughput) multiplied by the average time an item spends in the system (Cycle Time). It was proven by John Little in 1961 and applies to any queuing system — including software Kanban boards.

What units should I use for throughput?

Use items per day consistently. If your team completes 10 items per week, divide by 5 to get 2 items per day. The cycle time field must then also be in days for the formula to be dimensionally consistent.

What cycle time should I target?

Choose a cycle time that represents your service-level expectation — for example, the number of days by which 85% of items should be done. Common targets are 3, 5, or 10 business days depending on the work type.

Should I round the WIP limit up or down?

Round down (floor) for stricter flow control and shorter actual cycle times. Round up (ceiling) if your team is still maturing and a hard lower limit would cause frequent blocking. The tool shows both so you can choose.

Does this apply per stage or for the whole board?

Apply Little's Law per stage — each column on your board can have a different throughput and cycle time target. Run the calculator separately for each stage you want to cap.

Is my data saved anywhere?

No. All calculations happen in your browser. Nothing is sent to a server. The page resets when you navigate away.

WIP Limit Calculator

Name: WIP Limit Calculator
Availability: InStock
Author: Nham Vu

Enter your team's throughput and target cycle time to calculate the optimal WIP limit for any Kanban workflow stage using Little's Law.

Inputs

Little's Law: WIP = Throughput × Cycle Time

Throughput (items completed per day)

If weekly: divide by 5. Example: 10/week = 2/day.

Target Cycle Time (days)

Max days an item should spend in this stage.

Quick Presets

Enter throughput and cycle time, then click Calculate.

Recommended WIP Limit

—

Floor (stricter)

–

—

Ceiling (lenient)

items in-flight at any time

Formula Breakdown

WIP = —/day × — days = — items

What to do next

Set your Kanban column cap to the floor value for tighter flow control.
Use the ceiling value if the team is still maturing and hard limits would cause frequent blocking.
Re-run this calculator per stage — In Progress, Review, and QA may each have different throughputs.
If actual in-flight items consistently exceed the limit, investigate bottlenecks upstream.

Sensitivity: cycle time vs. WIP limit

Cycle Time (days)	WIP Limit (floor)

Summary

Enter your team's throughput and target cycle time to calculate the optimal WIP limit for any Kanban workflow stage using Little's Law.

How it works

Enter your team's average throughput — how many items (tasks, tickets, features) are completed per day.
Enter the target cycle time — the maximum number of days an item should spend from start to done.
The calculator multiplies the two values using Little's Law: WIP = Throughput x Cycle Time.
Review the recommended WIP limit and set it as the column cap on your Kanban board.
Adjust throughput or cycle time targets and see how the WIP limit changes in real time.

Use cases

Set the WIP cap for a development column so engineers are never overloaded.
Determine how many items a QA stage can hold before a queue builds up.
Plan Kanban board limits when onboarding a new team with no historical data.
Model the effect of hiring: see how WIP limit grows when throughput increases.
Identify bottleneck stages by comparing actual in-flight counts to the recommended limit.
Explain WIP limits to stakeholders with a concrete, formula-backed number.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu