Picking replenishment: minimums and maximums, reserve and pick bin

November 13, 2026 · 7 min read

A picker who reaches the bin and finds it empty has three options, and all three are bad: wait, go and fetch the goods from reserve themselves or leave the order incomplete. Picking replenishment exists so that this does not happen. This article explains what it is, how the minimums and maximums of each bin are set, when it pays to replenish and how to organize it so that the picker does not run out of goods.

What picking replenishment is

It is bringing goods down from reserve to the pick bin before the bin runs empty. It is an internal movement: the total stock of the warehouse does not change, it only changes place. But order picking not stopping depends on it.

It makes sense when the warehouse separates two kinds of bin. If all the stock of an item is in a single bin within arm's reach, there is nothing to replenish; as soon as there are pallets up high or boxes in a separate storage zone, somebody has to bring those goods to the picking zone in time.

Pick bin and reserve: differences

Swipe the table sideways to see all the columns →

	Pick bin	Reserve
Where it is	At hand height, on the lower levels and near the tables	On the upper levels or in a separate zone
What it holds	A small quantity, in units or open boxes	The bulk of the stock, on full pallets or in full boxes
Who touches it	The picker, on foot or with a cart	The forklift operator, with a machine
How often it is touched	On every order that includes that item	Only to replenish or to serve large quantities
How many per item	The usual is one fixed bin	As many as the stock needs

Having a fixed pick bin for each item helps: the picker always finds it in the same place and the minimums and maximums are set once. Which items deserve the best bins is covered in how to organize the locations in a warehouse.

How to calculate the minimums and maximums of a bin

Each pick bin carries two numbers: the minimum, which is the level below which you have to replenish, and the maximum, which is how far it is refilled.

The minimum has to cover what will be picked while the replenishment arrives. The calculation is:

→Minimum = the item's consumption per hour × the hours the replenishment takes + safety margin.
→Maximum = what fits in the bin without getting in the way, rounded to full boxes or pallets from reserve.
→Quantity to replenish = maximum − what is left in the bin.

An example with numbers made up only to show the calculation: if 20 units of an item are picked per hour in the busiest period and the replenishment takes one hour from the moment it is requested, the minimum has to be 20 plus the margin; with a margin of 10, 30. If 120 fit in the bin and 25 are left, 95 are brought down, or the full box that comes closest.

Two warnings. A minimum that is too low leaves the picker without goods; one that is too high fills the queue with small replenishments that keep the forklift operator busy for nothing. And the numbers are not forever: an item on promotion or in season is consumed faster, and its minimum has to go up with it. Before a peak it is worth reviewing them, as we explain in how to get your warehouse ready for peak season.

When to replenish

→By minimum: when the bin drops below its minimum, the replenishment is generated. It is the basic way and it works by itself if the stock by bin is up to date.
→By demand: before releasing a wave of orders, you look at which bins will not have enough to serve it and replenish them first, even if they have not yet broken the minimum.
→In quiet hours: first thing, last thing or between pickups, the bins are refilled up to the maximum, so that the busiest period starts with everything full.
→Emergency: the picker arrives and there are no goods. It should not happen; when it does, you need to know why.

The normal thing is to combine the first three and measure the fourth. Every emergency replenishment is a warning that a minimum is set wrong or that the stock in the software does not match the stock on the rack.

How to keep the picker from running out of goods

→Reliable stock by bin. Replenishment by minimums is triggered by the number in the software: if that number is wrong, the alert arrives late or does not arrive. Counts by bin keep it up to date.
→Replenishment ahead of other forklift tasks when there are orders waiting for that item.
→A single open replenishment per bin, so that two pallets are not brought down to the same place.
→Goods in reserve that are already committed to one replenishment must not be counted for another.
→Respect the batch: what expires first or what came in first is brought down first, according to the item's rule, and batches are not mixed in the bin without it being recorded.
→Scan origin and destination. A replenishment left in the bin next door creates two errors: one where goods are missing and another where there are too many.
→A button for the picker to report the shortage and carry on with the rest of the order, instead of standing waiting.

The rules for which batch leaves first are in FIFO, FEFO and LIFO, and how to count the bins without stopping the warehouse, in how to count stock with a PDA.

What quantity to bring down: loose units, boxes or full pallets

The calculation “maximum minus what is left” gives a number of units, but in reserve the goods are in boxes or on pallets. Splitting a pallet up high to bring down exactly what is missing costs time and leaves a remainder that then has to be counted. That is why the usual thing is to round: you bring down the full box or pallet that comes closest to the calculated quantity without exceeding what fits.

To make that rounding easy, it is worth sizing the pick bin with the reserve unit in mind: so that a full box plus the minimum fits, or a full pallet plus the minimum. If it does not fit, every replenishment will force you to split parcels or leave the surplus somewhere else, and surplus with no place of its own is the origin of a lot of lost stock.

When there are several pallets of the same item in reserve, the first one brought down is the one the dispatch rule points to —the one that expires first or the one that came in first— and, all else being equal, the pallet already started before a full one, so as not to leave remainders scattered across the upper levels.

What to measure in replenishment

→Shortages reported by pickers: how many times somebody reached a bin and there were no goods. It is the direct indicator that replenishment is arriving late.
→Time from the task being generated until it is confirmed: it is the real figure to use when calculating the minimum.
→Replenishments per item: one that is replenished many times a day calls for a bigger pick bin or a higher maximum.
→Bins that are never replenished: perhaps that item does not need such a good pick bin.

Common mistakes in replenishment

→Replenishing “when it looks empty”: by then there is already a picker standing still.
→Setting the same minimum for every item, whether it ships a lot or a little.
→The picker climbing up to get the goods: they lose time, leave the order half done and the movement is not recorded.
→Bringing the pallet down and not confirming it in the software: the bin is full, but the system keeps asking for it to be replenished.
→Replenishing at the height of the rush through the same aisles where picking is going on.

How we do it at Ubika

In Ubika each pick bin can carry its minimum and its maximum. When the bin drops below the minimum, the software generates the replenishment task by itself, for the quantity missing up to the maximum, and chooses which reserve bin to bring it down from. Those goods are committed to that replenishment, so they are not counted twice, and no second task is opened for a bin that already has one in progress.

The task reaches the forklift operator on the PDA as “Replenish”: bringing down from reserve to the pick bin what is running out. With automatic replenishment switched on, the software checks the minimums after every pick. In the office, the replenishment screen shows which bins are below the minimum, the pending tasks and the ones already done. And if a picker still finds the bin without goods, they report it on the PDA, a notification is sent to count that bin and they carry on with the rest of the order.

In the published prices, automatic replenishment is included from the Pro plan. You can see the rest of the software in warehouse management software and how work is done with the terminal in stock control with a PDA.

Frequently asked questions

What is picking replenishment?

It is the internal movement that refills the bins orders are picked from with goods brought from reserve, that is, from the pallets or boxes stored on the upper levels or in another zone. No stock enters or leaves the warehouse: it only changes bin.

What is the difference between the pick bin and reserve?

The pick bin is at hand height, holds a small quantity and is where the picker takes from. Reserve holds the bulk of the stock, normally on full pallets on the upper levels, and is only touched to replenish or to serve large quantities.

How do you calculate the minimum of a pick bin?

The minimum has to cover what will be picked from that bin while the replenishment arrives, plus a margin. As a formula: the item's consumption per hour × the hours the replenishment takes, plus the safety margin you decide.

How do you calculate the maximum?

The maximum is what fits in the pick bin without getting in the way or mixing. If a full pallet or box from reserve fits whole, the convenient thing is for the maximum to allow it to be brought down in one go without splitting it.

When do you have to replenish?

There are three usual moments: when the bin drops below the minimum, before releasing a wave of orders that is going to empty it, and in quiet hours, to leave the bins full before the next shift. The normal thing is to combine all three.

Who does the replenishment?

Normally a forklift operator, because reserve is usually up high and a machine is needed to bring it down. In small warehouses with no upper levels, the picking team itself does it in the gaps between orders.

Keep reading

What Ubika does: warehouse management software · software for 3PLs · WMS for e-commerce