Zone picking vs batch picking: how they work, how to choose

Summary

Zone picking and batch picking answer the same question in two ways: how to stop every picker walking the whole warehouse for every order. Zone picking splits the work by area: each picker stays in one zone, and an order passes through several zones or is merged from them. Batch picking splits the work by trip: one picker collects several orders in a single tour, so the walk is shared. Zones need even workloads and a consolidation step, while batches need orders that share stops, a route built for the batch and often a sort step.

Order picking is expensive. A 2023 paper in the journal Logistics puts it at up to 55% of the total operating costs of the warehouse, which makes the picking method a budget question.

Each method fixes one problem and creates a new job: consolidation for zones, sorting for batches. When that new job becomes the bottleneck, a switch that looked right on paper leaves throughput flat.

Which method fits depends on the order profile, the SKU count, the size of the building and the size of the team, and most sites end up running a hybrid of the two. Operations teams often raise the same complaint: batch picking went live and throughput did not move.

Zone picking vs batch picking: what is the difference?

The two methods divide different things. Zone picking divides the building between pickers, and batch picking divides the orders into trips. Zone picking shortens each person's walk, while batch picking cuts the number of walks.

What is zone picking?

Zone picking is an order picking method in which the warehouse is split into zones and each picker picks only inside an assigned zone. An order that needs items from three zones is picked by three people. Each picker's walk shrinks to the size of their zone.

Zones follow how the goods are stored and handled. Fast movers sit near the pack area, bulky items in pallet racking, small parts in shelving, and chilled or high-value goods in their own area. A zone can also be set by equipment, such as a reach truck area that only trained drivers enter.

The main design choice in a zone picking system is what happens to an order that crosses zones. There are two ways to handle it.

Sequential zone picking, or pick and pass

In sequential zone picking, the order tote travels from zone to zone, on a conveyor or a cart, and each picker adds the lines from their zone before passing it on. The order stays in one tote from start to finish, so nothing needs sorting at the end.

The slowest zone sets the pace: a tote waits at any zone that is behind, and an order with lines in five zones needs five hand-offs before it reaches packing.

Simultaneous zone picking, or pick and merge

In simultaneous zone picking, all zones pick their part of the same order at the same time, and the parts meet at a consolidation point before packing. Large orders finish faster because the zones work in parallel.

The extra work sits at the end of the line, where something has to merge the parts: a put wall, a sorter or a staging lane where totes wait for their partners. One missing tote holds a finished order back.

What warehouse zone picking needs to work

Zone picking pays only when the work per zone is close to even. A 2024 study in IFAC-PapersOnLine, on picking towers where each floor works as a zone, states that workload balancing among pickers "is crucial since it could lead to a lower makespan, idle time and tardiness". One overloaded zone holds up every order that passes through it.

Balance also has to be kept up. Demand moves between zones with the season, a new client or a promotion, and a zone plan that was even in March can be lopsided by November. Re-slotting the fast movers and moving people between zones during the shift are the usual fixes, and both take someone watching the numbers every week.

Zone picking also caps how many people share an aisle, because only the pickers of one zone enter it. That keeps traffic from other zones out, but inside a busy zone the density still builds.

What is batch picking?

Batch picking is an order picking method in which one picker collects the items for several orders in a single trip through the warehouse. If 12 orders each need one item from aisle 14, the picker visits aisle 14 once instead of 12 times.

The gain comes from shared stops and a shared walk. Two orders that need the same SKU, or SKUs in the same aisle, cost little more to pick together than one order alone. Two orders at opposite ends of the building save almost nothing when they share a cart.

That is why the way orders are grouped matters as much as the decision to batch. Our article on how order batching changes pick rates goes into the grouping logic.

Sort while picking or sort after picking

There are two ways to keep the orders apart. Sort while picking puts each order in its own tote or slot on the cart, which is how cluster picking works. Sort after picking collects everything into one container and splits it into orders at a sort station, which makes the walk faster and adds a second handling step.

Which of the two fits depends on order size, cart space and how much room there is for a sort area. Sort timing is its own decision, and the comparison of cluster and batch picking covers it in detail. Both count as batch picking here.

Batch picking and congestion

Batching reduces congestion because it reduces trips. One picker collecting eight orders per tour means fewer people in the aisles for the same volume. Congestion comes from too many pickers in a fixed number of aisles, so batching works on the cause.

A batch can raise the time one picker spends at a single pick face, because that picker fills several orders there. A large batch on a fast mover can hold up the aisle for a moment, which is a reason to cap batch size on the busiest locations.

Zoning contains the same congestion by splitting the traffic between areas, and pays for it with uneven zones and a merge step.

When should you use batch picking or zone picking?

The order profile decides more than the size of the building. Lines per order, how much orders overlap on SKUs and locations, the SKU count and the distance between picks come first. The team and the equipment you already have come second.

Small teams rarely gain from zones. With few pickers, either a zone sits empty while its picker helps elsewhere, or orders wait at hand-offs. Batching keeps everyone on the same kind of work, and the next free picker takes the next batch.

Large ranges and long pick paths push toward zones, especially when parts of the building need different equipment or training anyway. A pallet racking area worked by reach truck drivers is already a zone, whatever the WMS calls it.

The new job is where projects stall. A batch operation that adds a sort station has moved work from the aisles to the sort area, and a zone operation that adds a put wall has done the same. If that station cannot keep up at peak, throughput at the pack bench stays where it was.

A decision guide in five steps

1. Pull three months of order lines from the WMS. Count lines per order, units per line, and how many orders released in the same hour share a SKU or an aisle.
2. Mark the areas that need their own equipment, temperature or access rules. Those are zones already, whatever method runs elsewhere.
3. Check the team: if not every zone can be staffed on every shift, start with batching and add zones later.
4. Size the extra step each method needs, a sort area for batches or a merge point for zones, for the peak day and not the average.
5. Run the candidate method on historical orders before changing the floor, and compare travel per line, lines per hour and order lead time.

Step 5 is the one most often skipped. A model of your own layout and orders settles the question faster than a pilot on the floor, and you can simulate different warehouse scenarios before anyone moves a rack. Most sites then land on a mix of both methods.

Can you combine batch and zone picking?

Yes, and most larger operations do. Hybrid methods keep the short walk of zones and the shared trips of batches. Three are common, and wave planning often sits on top of them.

Zone-batch picking

Each picker works one zone and picks a batch of orders inside that zone on every trip. The zone keeps the walk short and the batch keeps the stops per order low. Orders that cross zones still need consolidating afterwards.

Pick and pass with batches

Totes travel from zone to zone and each zone adds its lines. How orders are batched and sequenced into the zones decides whether the line flows or queues.

A 2023 modelling study of pick-and-pass systems in Operations Research and Decisions found that "the most significant benefits were achieved by batching optimization", with storage and batching optimization together cutting total order-picking time by 35 to 45% against random policies.

The same study found that balancing the zones with random batching gave only a 10 to 20% improvement, so in that model the batches mattered more than zone balance.

Zone picking with consolidation

All zones pick their part of an order at the same time and the parts meet at a put wall, sorter or staging lane. It is the fastest way to finish a large multi-line order, and the most dependent on the merge point keeping up.

Where wave picking fits

Wave picking decides when orders are released. A wave releases a set of orders for a time window, often tied to a carrier cut-off, and those orders are then picked by batch, by zone or both. Our guide to wave picking covers how to plan the waves themselves.

Discrete and case picking, which sit outside this comparison, are in the complete guide to warehouse picking strategies.

Why hasn't batch picking improved throughput?

Operations teams describe it the same way: the warehouse moves to batch picking, trips per order drop, and shipped lines per hour barely change. In most cases the batches, the route or the sort step absorb the gain. Each one can be checked in the data.

1. The batches follow WMS rules

Most WMS batching groups orders by a simple rule: same carrier, same cut-off, same order type or a range of order numbers. Those rules group orders that ship together, which is a different thing from orders whose picks sit close together.

Two orders for the same carrier at opposite ends of the building share a cart and nothing else. A better batch is chosen by the stops the orders share, within the cart's capacity, its weight limit and the orders' cut-off times.

2. The route does not change with the batch

Many pick lists are printed in location order and walked in a serpentine through every aisle that holds a pick. A bigger batch on a fixed serpentine is a longer serpentine, with aisles walked end to end for a single item. The route has to be calculated for each cart, through the real layout.

Batching and routing also affect each other. The Logistics paper cited above warns that if the two are "addressed independently, there is a possibility of encountering a local, suboptimal, or even unacceptable solution". The batch should be chosen knowing the route it will produce.

3. The sort step became the bottleneck

Pick-then-sort adds a handling step, because every unit is handled twice: once into the batch tote and once into its order at the sort station. If the sort area is staffed for the average day, totes queue there at peak and the pack bench waits.

The sort station is the first place to look. When totes wait at sort, smaller batches or sorting on the cart will lift throughput more than any change in the aisles.

What an optimization layer adds on top of the WMS

Most of these fixes come down to two decisions: which orders share a cart, and the route that cart takes. The WMS holds the orders and the locations, but rule-based batches and location-order pick lists do not calculate either decision.

Optioryx Pulse sits on top of the existing WMS and builds the batch and the route together, within limits such as orders per cart, volume, weight and cut-off times. The result goes back to the WMS, so pickers keep their scanners and their routine. When clustering, routing and slotting are optimized together, walking distance falls by up to 50%.

A MedTech distribution center picks about 30,000 order lines a day with 60 operators, all on foot with trolleys. Before Pulse, operators chose by hand which orders to combine in the WMS, and the trolleys followed a general serpentine route.

Pulse clustered the orders onto each trolley first. The first measured result was a 15% increase in picking productivity, worth up to 9 FTE in the manual picking organization. Six weeks later, with route optimization and double-stacked trolleys added, productivity stood 27% above the period before any optimization software.

Bleckmann, a 3PL for fashion and lifestyle brands, runs route optimization alongside its existing WMS. Walking distance fell by an average of 15 to 20% compared to non-optimized routes.

The same two decisions exist in a zone layout. Inside each zone, someone still decides which orders share a tote and in which order the zone is walked, and the pick-and-pass study above found batching to be the biggest lever there.

When this will not help

Batching and routing software shortens the walk, so it helps least where the walk is already short. Four cases stand out:

• Goods-to-person and other automated sites, where the goods travel to the picker.
• Small teams with only a few pick tours a day.
• Sites where travel is already a small part of picking time. Replenishment, pick face layout or the confirmation step come first there.
• Operations with strict rules on which orders may share a cart. The fewer orders can be combined, the less there is to gain.

This can be checked on your own data before anything changes. Pulse runs on uploaded order history in the web app, without a WMS connection, and shows optimized batches and routes next to the current ones. Live operation does need the integration, so the test comes first and the integration after.

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