Should I reduce Little's law WIP for downtime or yield?

No. Average throughput over clock hours already includes every stop, and rejects are units that left the line. Discounting WIP again for uptime or yield counts the same loss twice.

Why does my WIP count not match the Little's law figure?

A count is a snapshot; Little's law gives the average. A count well above it usually means WIP is building, the count caught a stoppage, or your lead time leaves out queue time.

What throughput should I use on a two-shift line?

Use the same clock as your lead time. If lead time counts only working hours, divide output by working hours; if it includes units sitting overnight, divide by calendar hours.

How low can I set the WIP cap?

No lower than WIP being worked. At that floor lead time equals processing time and cannot shrink, so any further cut lowers output. Leave margin above it for stops.

Conveyors calculator

Little's Law WIP Calculator for Conveyor Lines

Find the average WIP on your line from throughput and lead time, and the WIP cap that meets a target lead time. Use it when setting kanban limits or pricing a WIP reduction.

What this calculator does

Average WIP on a conveyor line from throughput and lead time, and the WIP cap that meets your target.

Formula used

Little's law WIP = average throughput × average line lead time ÷ 60
WIP being worked = average throughput × processing time ÷ 60; WIP waiting = Little's law WIP − WIP being worked
WIP cap = average throughput × target lead time ÷ 60; WIP to remove = MAX(0, Little's law WIP − WIP cap)
WIP value = Little's law WIP × unit cost; cash freed = WIP to remove × unit cost

Inputs explained

Average Throughput: Units out ÷ hours on the lead time clock, stops included.
Average Line Lead Time: Mean entry to exit time per unit, from timestamps or tagged units.
Processing Time per Unit: Sum of each station's process time for one unit, from standard work.
Target Lead Time: The lead time you have promised or set for this line.
Average WIP Unit Cost: Standard cost of a unit partway through the line.

How to use the result

Best suited to setting a WIP limit for a conveyor line, pricing a WIP reduction before a kaizen event, checking a lead time promise against current WIP.
Measure over several shifts: a short window that starts and ends with WIP on the line biases the averages. A cap holds throughput only while the bottleneck stays fed; set it too low and output falls instead of lead time.

Current U.S. benchmarks

The U.S. has 21,668 machinery manufacturing establishments employing about 1,086,146 workers (Census County Business Patterns, 2023).

Common questions

Should I reduce Little's law WIP for downtime or yield? No. Average throughput over clock hours already includes every stop, and rejects are units that left the line. Discounting WIP again for uptime or yield counts the same loss twice.
Why does my WIP count not match the Little's law figure? A count is a snapshot; Little's law gives the average. A count well above it usually means WIP is building, the count caught a stoppage, or your lead time leaves out queue time.
What throughput should I use on a two-shift line? Use the same clock as your lead time. If lead time counts only working hours, divide output by working hours; if it includes units sitting overnight, divide by calendar hours.
How low can I set the WIP cap? No lower than WIP being worked. At that floor lead time equals processing time and cannot shrink, so any further cut lowers output. Leave margin above it for stops.

Last reviewed 2026-10-01.