Lead Time Estimate Calculator

Work out lead time estimate instantly with clear inputs, formula shown and shareable results.

About Lead Time Estimate Calculator

Manufacturing lead time is the sum of process, queue, move and inspection time. In most job shops queue dominates, often accounting for 80-95% of elapsed time, which is why lead time falls dramatically when WIP is reduced even though nothing about the machining gets faster.

Formulas

Lead time

Lead time = process + queue + move + inspection time

Value-added ratio

VA ratio % = process time x 100 / total lead time

Worked example

With the default values below, Lead Time Estimate Calculator returns Total Lead Time of 560.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Value-Adding Process Timeminimum 0 minutes: 45 minutes
Queue And Wait Timeminimum 0 minutes: 420 minutes
Move And Transport Timeminimum 0 minutes: 35 minutes
Inspection And Setup Timeminimum 0 minutes: 60 minutes

Results

Total Lead Time: 560.0
Lead Time In Hours: 9.333
Value-Added Ratio: 8.036%
Non-Value-Adding Time: 515.0

Step by step

1Values used
2Lead time
3Value-added ratio
4Total Lead Time= 560.0
5Lead Time In Hours= 9.333
6Value-Added Ratio= 8.036
7Non-Value-Adding Time= 515.0

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is queue time so large?

Queue grows non-linearly with utilisation. At 90% machine loading, average queue is around nine times the process time; at 95% it is nineteen times. High utilisation and short lead time are in direct conflict.

Is inspection value-adding?

Not from the customer's point of view — it is necessary waste. Building quality into the process so inspection can be reduced is a standard improvement route.