How do I measure queue time on a line?

Tag a unit at line entry and log when it reaches and starts each station. Minutes between reaching and starting are queue time; for one buffer, units queued ÷ the next station's rate gives it.

Why does the WIP figure differ from what I count on the floor?

Little's law gives average WIP at a steady rate, so a count taken during a stop or a surge will differ. A steady count above it means units spend longer on the line than your element times add up to.

What is the difference between lead time and cycle time?

Cycle time is how long a station takes to repeat its work on one unit; lead time is how long one unit takes through the whole line. A line with 60-second cycles can still have a 50-minute lead time.

Should conveyor transfer time count as waste?

Yes, in lean terms: conveyance moves the unit without changing it, so it lowers flow efficiency. Shorter layouts and fewer transfers cut it, though some movement between stations is unavoidable.

Conveyors calculator

Lead Time Through Line Calculator

Add processing, transfer, queue and hold minutes to get lead time through the line, then see its flow efficiency and WIP. You need a traced unit's timings and the line's output rate.

What this calculator does

Minutes a unit spends from line entry to exit, how much of it is processing, and the WIP that lead time holds.

Formula used

Lead time = processing + conveyor transfer + queue and buffer + inspection and hold time
Flow efficiency = processing time ÷ lead time × 100
Non-processing time = lead time − processing time
WIP on the line = line output rate × lead time ÷ 60 (Little's law)
WIP waiting in queues = line output rate × queue and buffer time ÷ 60

Inputs explained

Processing Time: Value-added minutes at stations along the route, machine time included.
Conveyor Transfer Time: Minutes moving between stations, through elevators, turns and merges.
Queue and Buffer Time: Minutes waiting in queues and accumulation zones, from a tagged-unit trace.
Inspection and Hold Time: Checks, scans, release holds and paperwork minutes for one unit.
Line Output Rate: Units leaving the line per hour, averaged over a shift.

How to use the result

Best suited to building the timeline of a value stream map, choosing which delay to attack first, estimating line WIP at a new output rate.
Averages hide spread: a unit caught behind a long stop waits far longer than this lead time. Covers the line only, not order entry, raw material or finished goods storage.

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

How do I measure queue time on a line? Tag a unit at line entry and log when it reaches and starts each station. Minutes between reaching and starting are queue time; for one buffer, units queued ÷ the next station's rate gives it.
Why does the WIP figure differ from what I count on the floor? Little's law gives average WIP at a steady rate, so a count taken during a stop or a surge will differ. A steady count above it means units spend longer on the line than your element times add up to.
What is the difference between lead time and cycle time? Cycle time is how long a station takes to repeat its work on one unit; lead time is how long one unit takes through the whole line. A line with 60-second cycles can still have a 50-minute lead time.
Should conveyor transfer time count as waste? Yes, in lean terms: conveyance moves the unit without changing it, so it lowers flow efficiency. Shorter layouts and fewer transfers cut it, though some movement between stations is unavoidable.

Last reviewed 2026-10-01.