What window should I average WIP and throughput over?

One several times longer than the lead time you expect, so jobs that start and finish inside it dominate. Use the same window for both, and skip ramp-ups, shutdowns and holiday weeks, when WIP is building or draining.

Why does measured lead time differ from WIP ÷ throughput?

Usually the window or the scope differs. If WIP grew during the window, starts exceeded finishes and the balance the law needs fails. If your count includes raw stock or finished goods, it covers more than the line.

Will halving WIP halve lead time?

Yes, while throughput holds. It holds as long as the bottleneck still has work waiting; once it starves, output falls with WIP and lead time stops improving. Cut WIP in steps and watch daily output.

Can I use dollars instead of units?

Roughly. WIP at cost divided by cost of goods finished per day gives days. Part-built units carry only part of their cost, so the result runs short when much of the cost is added along the line. Never divide dollars of WIP by units per day.

Lean Manufacturing & Operations calculator

Lead Time From WIP Calculator

Read the lead time your WIP implies before you quote a date or set a WIP cap. You need average WIP, daily throughput and the lead time you have promised.

What this calculator does

Average lead time through a line from the WIP it holds and the rate it finishes work, checked against your target.

Formula used

Lead time = WIP ÷ throughput (Little's law)
WIP at target lead time = throughput × target lead time
WIP over target = WIP − WIP at target lead time
Throughput needed for target = WIP ÷ target lead time

Inputs explained

Work in Process: Average units released and not yet finished across the line.
Throughput: Good units finished per day over the same window.
Target Lead Time: The lead time you quote or have committed to hold.

How to use the result

Best suited to checking a quoted lead time against the floor, setting a WIP cap for a pull loop, showing the lead time a WIP cut saves.
Assumes throughput holds as WIP falls; once the bottleneck runs out of work, output drops instead of lead time. Gives the average: single jobs can take much longer when priorities change.

Current U.S. benchmarks

U.S. manufacturing runs at 75.7% of capacity (Federal Reserve, Aug 2026). New factory orders are up 8.5% year over year (Census).

Common questions

What window should I average WIP and throughput over? One several times longer than the lead time you expect, so jobs that start and finish inside it dominate. Use the same window for both, and skip ramp-ups, shutdowns and holiday weeks, when WIP is building or draining.
Why does measured lead time differ from WIP ÷ throughput? Usually the window or the scope differs. If WIP grew during the window, starts exceeded finishes and the balance the law needs fails. If your count includes raw stock or finished goods, it covers more than the line.
Will halving WIP halve lead time? Yes, while throughput holds. It holds as long as the bottleneck still has work waiting; once it starves, output falls with WIP and lead time stops improving. Cut WIP in steps and watch daily output.
Can I use dollars instead of units? Roughly. WIP at cost divided by cost of goods finished per day gives days. Part-built units carry only part of their cost, so the result runs short when much of the cost is added along the line. Never divide dollars of WIP by units per day.

Last reviewed 2026-10-01.