How do you calculate total lead time?
Add every stage between placing an order and the stock being sellable: your processing, supplier production, transit, customs clearance and your own goods-in handling. The supplier quoted figure covers only production, so planning against it understates the real wait, often by weeks.
Lead Time Calculator formula
Total lead time = Order processing + Supplier production + Transit + Customs + Goods-in
Worked example: 2 + 14 + 21 + 3 + 2 days is 42 days total, against a supplier quoted 14 days, meaning 28 days are invisible unless you count them.
How this works in your browser
Stages are summed into a single total, with each kept separate rather than collapsed into one field. That separation is the whole value: seeing that customs and goods-in together add a week to a supplier's quoted production time is what makes the total credible and shows you which stage to work on. The output is intended to feed directly into the reorder point calculation, where lead time is the multiplier on daily demand. Everything runs in your browser.
Who uses Lead Time Calculator
Setting reorder points
Feed a realistic lead time into stock triggers instead of a quoted one.
Comparing suppliers
Judge suppliers on total delivered lead time, not quoted production time.
Finding delays
See which stage of the chain is actually costing you the most days.
Planning seasonal buys
Work backwards from a peak to know when orders must be raised.
Frequently asked questions
Why is my actual lead time longer than the supplier quotes?
Because a supplier quotes their own production window, which typically excludes order approval on your side, transit, customs clearance, and the days between goods arriving and being checked in and sellable. Adding those stages usually reveals a total considerably longer than the quoted figure.
Which stage should I attack first?
The longest one, obviously, but also the most variable one. A stage that is consistently ten days is easier to plan around than one that swings between two and twelve, and variability is what forces you to carry safety stock. Reducing variance is often worth more than reducing the average.
Should I use average or worst-case lead time?
Average for planning normal order cadence, worst case for setting safety stock and reorder points. Planning everything on averages guarantees you stock out roughly half the time, which is rarely the intent.
How does lead time affect how much stock I hold?
Directly and expensively. Longer lead times mean more demand to cover while waiting, so both the reorder point and the safety stock rise. Halving lead time is one of the most effective ways to free up working capital tied in stock.
Is my supply chain data uploaded?
No. Everything is calculated in your browser.