Fixed, chaotic or mixed location storage in the warehouse: what each one is and when to use it

November 13, 2026 · 7 min read

When you set up a warehouse there is one thing to decide before almost everything else: whether each item has its own place or goods go wherever there is a free bin. The first is called fixed location storage; the second, chaotic or random location storage. In practice most warehouses end up somewhere in between, with mixed storage. This article explains what each one is, what it gives and what it takes away, when it makes sense and what you have to ask of the software for it to work.

What fixed location storage is

With fixed locations each SKU has a reserved bin. Item 1234 lives in aisle 2, bay 5, level 1, and nothing else is stored there. People learn it by heart, you can work from a paper list and anyone can see at a glance that a bin is empty.

The price is space. Each bin has to be sized for the maximum quantity of its item, so there is almost always air. If a SKU runs out, its bin stays empty even if the goods that have just arrived do not fit in the receiving area. And every time a new SKU comes in or an old one is discontinued, you have to rearrange by hand.

What chaotic or random location storage is

With chaotic storage the item has no place of its own. Whatever comes in is stored in a free bin that meets the rules —it fits, it does not mix what must not be mixed— and the software records which quantity has been left in which bin. To take it out, the software says where to go.

The name is misleading: there is no chaos, there is an order you cannot see. The same item can be in three different bins and have anything else next to it. In return, the building is used much better, because no bin sits waiting for one particular SKU, and adding a new item does not force you to move anything.

It has one condition that is not negotiable: without a record by bin, there is no warehouse. If someone stores a pallet and does not record it, that pallet is lost until someone stumbles on it. That is why random storage always goes hand in hand with labeled bins and a scan on every movement. If the bins are not numbered yet, start with how to organize and number the locations and with location labels with barcodes.

What mixed location storage is

Mixed storage splits the building into two parts with different rules:

→Picking bins, low down and at hand height, with a fixed or nearly fixed place for what sells most. The picker always picks from there.
→Reserve, up high or at the back, in random locations. That is where the bulk of the goods goes, in pallets or full boxes.
→Replenishment between the two: when the picking bin drops below a minimum, goods are brought down from the reserve.

This brings together the best of each system: short routes that are easy to learn in picking, and good use of space in the reserve. What needs care is replenishment: if it arrives late, the picker finds the bin empty with the goods three meters up.

Fixed or chaotic storage: differences, advantages and drawbacks

Swipe the table sideways to see all the columns →

	Fixed	Chaotic (random)	Mixed
Where each item goes	Always in its bin	In any free bin that is valid	Picking in its place; reserve wherever there is a bin
Use of space	Low: empty bins waiting	High	High in the reserve
Learning where each thing is	Easy, by heart	You do not learn it: the software says	Easy in picking
Adding and removing SKUs	Force you to rearrange	Do not force you to move anything	Only affect the picking area
What it requires	Little: you can run it with a list	Software with stock by bin and scanning	The same, plus replenishment
Main risk	Running out of space	Losing goods if they are not recorded	Replenishment that arrives late

When to use fixed, chaotic or mixed storage

Fixed fits when there are few SKUs, the catalog is stable and there is space to spare. Also in particular spots of any warehouse: tools, packing supplies or very bulky items that only fit in one place.

Chaotic fits when there are many SKUs, the catalog changes often, quantities go up and down with the season or goods from several clients are stored. A third-party logistics provider cannot reserve fixed bins for each client without half the building standing empty.

Mixed is the usual answer when orders are picked by the unit: the picker needs to find what sells most always in the same place, and the reserve needs to make use of the height. To decide which items deserve a picking bin in the best area, you use ABC analysis.

What the software needs in order to work with chaotic storage

Random storage works as well as the software that runs it. Before choosing one, check that it does this:

→It keeps stock by bin, not just by item: what there is, how much and where.
→It proposes the bin when putting away, with a criterion you can choose, and lets you pick another one if needed.
→It requires scanning the item and the bin when putting away and when picking. Without scanning, the record drifts within a few days.
→It knows what fits in each bin and does not send goods to a full one.
→It respects the no-mixing rules: different batches, different clients or families that cannot be together.
→It orders what goes out with a rule (first in, or first to expire) when the same item is in several bins.
→It generates the replenishment of the picking bin without anyone having to remember.
→It lets you count by bin without closing the warehouse, to correct differences in time.

The outbound rules are in FIFO, FEFO and LIFO, and the way to count without stopping, in cycle counting.

How to move from fixed to chaotic storage

You do not need to empty the building. The order that hurts least is this: number and label every bin; load into the software what is in each one, counting it; start putting away with a scan everything that comes in from that day on; and leave the picking area as it is until the record can be trusted. Then you decide which items keep a picking bin and which move to the random reserve. What you cannot do is stop storing things “where they always go” before scanning is up and running.

How we do it at Ubika

Ubika keeps stock by client and by bin. When goods are received, the PDA proposes the bin to put them away in and asks you to scan the item and the bin where it is left; if the bin is not a storage bin or the goods do not fit, it says so. The operator can put away in a bin other than the proposed one by scanning it.

The criterion used to propose the bin is chosen in the settings, from four: by ABC turnover (what sells most, low down and near; what sells least, up high), the free bin nearest to receiving, by zone (where that item, its family or its client already are) or consolidating next to the same item while it fits. All four respect what fits in the bin, not mixing batches and the families marked as incompatible, which do not share a bay.

For the mixed part, picking bins are given a minimum: when they drop below it, the software creates the replenishment task from the reserve. And if you have to rearrange, stock can be moved from one bin to another.

You can ask for the demo with your data or first see what it does in warehouse management software and in stock control with a PDA.

Frequently asked questions

What is fixed location storage in a warehouse?

It is the system in which each item has an assigned bin, always the same one. If the bin is empty, it stays empty until that item arrives again. It is easy to learn, but it wastes space.

What is chaotic or random location storage?

It is the system in which goods are stored in any free bin that meets the rules (it fits, it does not mix what must not be mixed). The item has no place of its own: the software records where each quantity has been left and says so when someone has to go and get it.

Why is it called a chaotic warehouse if it is in order?

Because at first sight it follows no order by family or by SKU: the same item can be in three bins and anything else can sit next to it. The order exists, but it is in the software and not in people's memory.

What is mixed location storage?

It is combining the two: fixed picking bins, low down and within reach, for what sells most, and a reserve in random locations for the rest of the goods. When the picking bin drops below a minimum, it is replenished from the reserve.

Can you run a chaotic warehouse without software?

Not reliably. Without a record by bin that is updated on every movement, nobody knows where each thing is. Random storage requires labeled bins, a scan when putting away and when picking, and software that keeps stock bin by bin.

Which system suits a small warehouse?

With few SKUs and space to spare, fixed locations work and are the simplest. As soon as the catalog grows, changes often or space runs short, the usual step is to move to mixed: fixed picking for what sells most and a random reserve.

Keep reading

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