Replenishment

Supplier lead time, and why yours is probably too short

One number in one field decides every order deadline you have. It is usually the only number in the whole setup that nobody checks.

Marcus VolstedCo-founder, Restocio Published 6 September 2026Updated 6 September 20266 min read

Supplier lead time, and why yours is probably too short

Your supplier's lead time is not how long the goods spend travelling. It is the whole span from the moment you place the order to the moment the stock is sellable on your shelf. Type the shipping time into a replenishment tool and every deadline it gives you arrives late by exactly the number of days you left out. Nothing warns you, because the tool is doing the arithmetic you asked for.

Understating lead time fails in a particular way. You order when the tool says to order, the order is placed on time, the supplier ships on time, and you still run out. Everyone involved did their job and the shelf is empty anyway.

The five segments of a real lead time

A lead time is five spans stacked end to end. Merchants reliably count one of them.

Segment	What it covers	Who controls it	Usually counted?
Order confirmation	From sending the purchase order to the supplier accepting it and putting it in the schedule	Supplier	Rarely
Production	Making the goods, if they are not already sitting finished in a warehouse	Supplier	Sometimes
Transit	Port to port, or door to door if your forwarder quotes it that way	Forwarder	Almost always. This is the one people mean
Customs and clearance	Entry, duty, inspection if you are selected for one	Broker and customs	Rarely
Putaway	Unloading, counting, and making the stock live in your store	You	Almost never

The three that go missing

Production. If your supplier makes to order, the clock starts when your deposit clears, not when the goods ship. This is the largest omission and the easiest to miss, because the same supplier often does both. A factory with a catalogue will ship stocked items in days and made-to-order items in weeks, and one average across both is wrong for every product it touches.

Clearance. Normally days rather than weeks, so it gets rounded to zero. It is also the segment with the worst tail: most shipments clear quickly and the occasional one sits for a fortnight, and you cannot tell in advance which is which.

Putaway. A container that lands on a Friday and gets counted the following Wednesday is five days of stock you thought you had. If receiving happens weekly rather than on arrival, that gap belongs in the number.

Where to put the days your supplier is usually late

Most merchants who have worked with a supplier for a while know they run roughly two weeks behind. The instinct is to hold a bit more safety stock to cover it. That feels like the same thing as adding two weeks to the lead time. It is not, and the difference is worth understanding before you choose.

Both placements hold the same quantity on the shelf. What changes is what the system believes. Your order deadline is calculated from the lead time, so putting the delay there moves the deadline earlier by the same two weeks and the order goes in sooner. Putting it in the buffer leaves the deadline where it was, and the extra stock quietly absorbs the lateness instead.

That distinction matters most in any tool that chooses between shipping routes for you, ours included, because the comparison it runs is days of stock left against days until arrival. Hide the delay in the buffer and that comparison sees a shipment that arrives on time. It will not suggest moving units to a faster route, because on the numbers it has, nothing is late. You end up with the extra stock and without the warning.

One caution in the other direction. If you add the delay to the lead time and leave your old safety buffer alone, you are now carrying it twice. Move it, do not copy it.

Measure it instead of asking for it

Suppliers quote the lead time they hope for. You already have the data to check, and it needs nothing new: the date you placed the order, and the date you counted the goods in. Those two timestamps bracket the whole thing, all five segments, with no need to split it apart.

Three completed orders is enough to spot a pattern and not enough to calculate percentiles honestly, so treat early numbers as a range rather than a figure. Watch the spread as much as the average. A supplier that averages 70 days because it is always 70 is a different proposition from one that averages 70 because it is usually 60 and occasionally 110, and the second one is why safety stock exists.

Season matters too. Factory shutdowns move lead times by weeks, not days, and they are on a calendar you can read in advance: Chinese New Year, Golden Week, Tet in Vietnam, Diwali in India. An order placed a fortnight before a shutdown does not get made a fortnight before a shutdown.

How this works in Restocio

Production days sit on the supplier, with a per-product override for the made-to-order exceptions, and they feed both the order deadline and the quantity rather than sitting in a notes field. Once a supplier has at least three receipts inside the last year, the app measures the real door to door time from your own purchase orders and shows it beside the number you typed.

It does not overwrite your number. That is deliberate: a measured average is evidence, and the decision about what to plan on stays yours. The honest limit of this is that measurement tells you a supplier slipped and never tells you why, so a one-off caused by a port strike looks identical to a supplier who has quietly got slower. Three data points cannot separate those, and neither can we.

Common questions

What should be included in supplier lead time?

Everything between placing the order and the stock being sellable: order confirmation, production if the goods are made to order, transit, customs clearance, and your own putaway. Most merchants count only transit, which is why their order deadlines fire late.

Is lead time the same as shipping time?

No, and treating them as the same is the most common error in this field. Shipping time is one segment of the lead time. On an import from Asia with made-to-order goods, production alone can be as long as the sailing.

Should I add my supplier's typical delay to the lead time or to safety stock?

To the lead time. Both hold the same amount of stock, but only the lead time moves your order deadline earlier, and only the lead time tells a system that decides between shipping routes that a shipment is going to be late. Put the delay in safety stock and the system believes every shipment arrives on time. Move the days rather than copying them, or you count the same margin twice.

How many completed orders do I need before a measured lead time is trustworthy?

Three is enough to see a pattern and to catch a badly wrong typed value. Percentiles need closer to eight or ten receipts before they mean anything, so with a small sample use the range from fastest to slowest rather than an average with a decimal point on it.

Why does my lead time change during the year?

Factory shutdowns and peak season. Chinese New Year, Golden Week, Tet and Diwali stop production for one to several weeks, and the ramp back up is slower than the shutdown itself. Freight has its own peaks, usually before those holidays and before Western Christmas, when space is scarce and sailings get rolled.

Marcus Volsted

Co-founder, Restocio

Marcus co-founded Restocio and works on it daily with a Swedish importer who plans their purchasing in it every working day. Restocio is built in Sweden by two founders, one Swedish and one Danish, and Marcus is the Danish one. Most of the examples on this blog come from that store's real ordering decisions rather than from a textbook. Why we are building it.