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Zone Picking: Pick-and-Pass, Parallel Layouts, and Balancing Work
Zone picking keeps each picker in one area so they walk less. See how pick-and-pass and parallel zoning work and how to balance zones to avoid bottlenecks.
6 min read
· Updated
November 2026
At a glance
How it works
In zone picking, the pick area is split into zones with pickers assigned to each. Orders pass from zone to zone in totes, or are picked in parallel and merged.
Where it fits
Large pick areas, many SKUs, and multi-line orders that would otherwise send one picker across the whole building. Often paired with conveyors and pick to light.
The hard part
A zone system is only as fast as its busiest zone. Uneven workloads create bottlenecks, and parallel zones add a consolidation step before shipping.
Zone picking is an order picking method that divides the pick area into zones and assigns each picker to one zone. Each order either passes from zone to zone in a tote, or several zones pick their parts in parallel and the parts are merged before shipping. It cuts walking in large pick areas.
In a large pick area, picking one order at a time sends every picker across the whole building. Pickers crowd the same aisles, nobody learns the locations well, and long multi-line orders take a full lap each. Zone picking keeps each picker in a smaller area. The catch is that orders now cross zones, so the zones have to stay balanced and the parts of each order have to come back together.
This guide covers the two forms of zone picking, when zones fit, how to size and balance them, how to measure them, and how robots are changing zone design. For a comparison with discrete, batch, cluster, and wave methods, see the order picking methods guide.
How zone picking works
A widely cited review of order picking research lists the advantages of zoning: each picker covers a smaller area, traffic congestion drops, and pickers become familiar with the item locations in their zone. Its main disadvantage is that orders are split and must be consolidated before shipment. There are two main ways to run it.
Pick-and-pass (progressive zoning)
Each order is assigned to a tote or carton that moves from zone to zone on a conveyor or cart. Pickers in each zone add their lines and pass it on, and a tote can skip any zone where it has nothing to pick. Because one container collects the whole order, order integrity is maintained and no sorting or product consolidation is required. Research describes these systems as often applied in ecommerce warehouses handling orders with a large number of order lines.
Parallel (synchronized) zoning
Pickers in several zones start on the same order at the same time, and the parts are merged afterward at a consolidation point. Orders finish sooner because zones work at once, but you need a merge step and a way to know when every part has arrived. Parallel zones are often combined with batch picking and released in waves so that each zone works the same set of orders.
When zone picking fits
Large pick areas. Where walking the full area for every order would dominate picker time.
Multi-line orders. Orders that touch several areas of the building.
Mixed storage types. Separate zones for shelving, flow rack, and bulk let you match equipment and training to each area.
Enough volume per zone. Each zone needs steady work, or pickers stand idle waiting for totes.
Zones fit poorly in small operations with only a few pickers per shift, where handoffs cost more than the walking they save. They also struggle when order mix swings so much that yesterday's zone boundaries are wrong today.
SKU fit check
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How to size and balance zones
If one zone holds most of the fast movers, totes queue in front of it while pickers in other zones wait. Balancing is the main design job.
Balance by work, not floor space. Use lines and units per zone from recent order history, weighted by how long each pick takes. Warehouse slotting decides which SKUs land in each zone, so treat slotting and zoning as one decision.
Plan for the merges. In conveyor-based pick-and-pass, research finds that the maximum throughput capability of a zone picking system is largely determined by the performance of the merges, where totes from each zone rejoin the main line.
Let work float between pickers. Fixed zones balance work only on average. In a bucket brigade, zone boundaries are not fixed: each picker works an order forward until the next picker takes it over, then walks back to take over work from the picker behind. Faster pickers end up covering more of the line, so work shifts toward them without a planner redrawing zones.
Revisit before peak. Seasonal and promotional mix shifts move work between zones. Recheck the balance on fresh order data before each peak.
How many zones
Start with the pickers you staff on a normal shift and the lines each zone can absorb without idle time or queues. Order size matters too. A study of robot-supported zone picking found that few zones are particularly good for large store orders, while many zones are particularly good for small online orders. If you serve both channels from one pick area, test whether different zone setups by shift or by order type beat a single compromise.
In parallel systems, size the consolidation point as carefully as the zones. Decide where partial orders wait, how you know an order is complete, and what happens when one zone runs late. A put wall or a simple hold location per order both work if the rule is clear.
Fit call
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How to measure zone picking
Lines per labor hour by zone. Large gaps between zones mean the zones need rebalancing.
Picker idle time. Minutes pickers spend waiting for totes, a sign of a bottleneck upstream.
Tote queue length. Totes waiting at each zone's entry point show where the line backs up.
Order cycle time. Time from first zone to complete order, including consolidation in parallel systems.
Accuracy by zone. Errors that cluster in one zone often point to slotting, labeling, or training there.
Roll these up to building-level measures such as lines picked and shipped per person hour. The warehouse KPIs guide has more definitions.
How automation changes zone picking
Conveyors. The classic pick-and-pass backbone. They move totes reliably at high volume but fix the layout; see conveyor systems in warehousing.
Pick to light. Lights at each location show which slot to pick and how many units, which suits short, dense zones. See the pick to light guide.
Robots in place of conveyors. In human–robot collaborative picking, pickers stay within their zone while robots transport order totes between zones. A 2024 Decision Sciences study found that a fixed zone-switching strategy that takes advantage of changes in the order profile could raise throughput by 17% compared with no zoning, at a higher robot cost.
Robots that pick. A robot can work its own zone, such as a slow-mover area or an overnight shift, as long as it can reach and grip the items stored there. See robotic picking systems.
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Where Avatar fits
Avatar's robots work in your existing racks, shelving, and bins with no re-racking or facility redesign. In a zone picking layout, a robot can be assigned a zone within your current footprint, and Avatar also handles carting (moving material) between areas. For very high, steady pick-and-pass volume, a conveyor-based system may still be the better fit. See where Avatar works on the Avatar solutions page.
Frequently Asked Questions
What is zone picking?
Zone picking is an order picking method where the pick area is divided into zones and each picker works only in their own zone. Orders either pass from zone to zone in a tote, or several zones pick their part of an order at the same time and the parts are merged before shipping.
What is pick and pass?
Pick and pass, also called progressive zoning, is a form of zone picking in which an order tote travels from zone to zone, usually on a conveyor. Each picker adds the items stored in their zone and passes the tote on, skipping zones with nothing to pick. Because one tote holds the whole order, no separate consolidation step is needed.
How many zones should a warehouse have?
Enough that each zone has steady work and none becomes the bottleneck. Start from lines per zone in your order history and the number of pickers per shift. Research on robot-supported picking found that fewer zones suit large orders and more zones suit small online orders, so the best count depends on your order mix.
Does zone picking require a conveyor?
No. Pick-and-pass systems often use conveyors, but totes can also move between zones on carts or mobile robots, and parallel zoning only needs a consolidation area. Conveyors suit high, steady volume, while carts and robots are easier to change when the layout or order mix shifts.
Sources
1. de Koster, R., Le-Duc, T., & Roodbergen, K. J. (2007). Design and control of warehouse order picking: A literature review. European Journal of Operational Research, 182(2), 481–501.
2. van der Gaast, J. P., de Koster, M. B. M., & Adan, I. J. B. F. (2018). Conveyor merges in zone picking systems: A tractable and accurate approximate model. Transportation Science, 52(6), 1428–1443.
3. Azadeh, K., Roy, D., de Koster, R., & Ghorashi Khalilabadi, S. M. (2024). Zoning strategies for human–robot collaborative picking. Decision Sciences. Abstract via Indian Institute of Management Ahmedabad.
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