Splitting Black Friday Inventory Coast to Coast.

Peak inventory is on its way, and you have two warehouses to fill, one on each coast. Someone has to decide how many units of each SKU go where, and the easiest answer is half and half. It feels balanced. It also tends to leave one coast short by mid-December.

A better peak split is decided SKU by SKU, based on where your orders actually ship. Map last year's Q4 orders and your recent orders to the closest warehouse, split only products that sell steadily on both coasts, and give each warehouse its own safety stock. We work through exactly this process for brands running bi-coastal fulfillment every peak season.

This hands-on Q4 playbook covers:

Why does a 50/50 inventory split usually misallocate peak stock?

A 50/50 split assumes customers are spread evenly across the country, and very few brands' customers are. Demand clusters where people live, where your ads run, and where the brand got its start, so one coast usually carries more orders.

The common mistake is splitting on full-year averages. Gift orders often ship to different regions than everyday orders, and a holiday promo on one channel can pull demand toward one coast. Last year's Q4 usually predicts this year's Q4 better than your annual numbers do, which is why the split starts with last Q4's orders. If you haven't pulled that data together yet, our 2025 peak data breakdown is a good place to start.

How do you map order destinations to each warehouse?

Export the last 90 days of orders plus last year's October through December, with ship-to state or ZIP and units per SKU. Assign each destination to the warehouse with the lower shipping zone for that address. A shipping zone is the carrier's distance band between origin and destination that drives ground rates and transit times — UPS publishes a definition of shipping zones that most carriers follow.

While you build it:

• 1Count units shipped, not customers. A buyer placing three supplement orders counts as one customer but three units of demand.
• 2Use ship-to addresses, since gift orders don't ship to the buyer. A holiday gift set's destination state is the one that matters for split.
• 3Flag central states where both warehouses land in similar zones. Those states are the easiest to assign slightly off and the hardest to catch later.

Those central states are the easiest to get wrong. Defaulting them to one side can skew the whole split, so compare transit times from both warehouses and assign each state to the faster one. The result is a demand share per coast, and the next question is which products should follow it.

Which SKUs should you split between two warehouses?

Split fast movers and keep slow movers in one warehouse. A product selling a few units a day leaves both buildings with thin stock when split, so each sells out sooner than one pooled supply would.

Bundles are easy to miss. A holiday gift set needs every component in the same building, so split its parts together or not at all. (We cover this in more depth in our gift-set kitting timeline if bundles are a meaningful share of your Q4 catalog.) With the split list set, you can put numbers on it.

How do allocation ratios and per-warehouse safety stock work?

Each split SKU gets its own East/West ratio from your Step 1 data, plus safety stock in each warehouse. Here's an illustrative example for a supplement brand's top 10 SKUs, using a flat 20% buffer per warehouse as a simple starting point:

Illustrative figures, not client data. Your buffer should come from your own demand swings and restock lead time.

The electrolyte packs are the one SKU where 50/50 is right, and only because the data says so.

Look at the totals, though: 3,890 units of buffer across both warehouses, the same amount one building would hold at 20%. That's where flat percentages mislead.

In one building, a slow week on one coast offsets a spike on the other. Split the stock and each warehouse has to absorb its own spikes, so a split usually needs more total buffer than one building would. Treat the flat percentage as a floor, and expect one coast to run out of something first anyway. (If you haven't built your base forecast yet, our SKU forecasting playbook covers that step before you get to the split.)

What happens when one warehouse sells out first?

When one warehouse runs out of a SKU, orders for it can route to the other warehouse. The order still ships, but it crosses more zones, so it costs more and arrives later.

Planning ahead means:

• 1Confirm your order routing falls back to the other warehouse automatically. If it doesn't, the order stalls until someone reassigns it manually.
• 2Set reorder triggers per warehouse, not just for total stock. A pull of 400 units from one coast triggers a transfer even if total inventory looks fine.
• 3Adjust site delivery estimates when fallback routing kicks in. An order shipping from across the country spends more days in transit, so the last day to order for Christmas comes sooner.

Holiday shipping cutoffs need extra attention here. An order shipping from across the country spends more days in transit, so the last day to order for Christmas delivery comes sooner. If your site's delivery dates don't account for that, some gifts will arrive late.

And if orders keep shipping from the far warehouse for weeks, it may be time to move stock.

When is a mid-season inventory transfer worth it?

A transfer pays off when the extra shipping cost of fallback orders for the rest of the season exceeds the cost of moving the stock, and the stock can arrive while demand is still there.

For the rough math, estimate how many orders you'll keep shipping from the far warehouse, multiply by the extra cost per order, and compare that to transfer freight plus receiving fees. Timing matters too — cross-country freight takes days to arrive and get received, the same lag you'd plan around as when creating and processing a transfer between any two warehouse locations. Transfers tend not to pay off:

• 1When the stock would land after December demand drops.
• 2When the quantity is too small for the savings to cover freight.
• 3When the receiving warehouse has a peak receiving backlog.

Each of those decisions is easier when you can see both warehouses' stock in real time. Our Glasshouse inventory platform surfaces both buildings in one view so fallback and transfer decisions run on live numbers instead of last week's spreadsheet.

Peak allocation should be decided SKU by SKU

Your order data already knows where your customers are. A split built from that data will beat a 50/50 guess every time.

Running it is the harder part: two inventory pools, two sets of reorder triggers, fallback routing, and transfer calls, all during the busiest weeks of the year. That's the work Nice Fulfillment takes on. Our Charleston and Salt Lake City warehouses route each order to the closest location automatically, with real-time inventory visible across both through Glasshouse, so fallback and transfer decisions run on live numbers instead of last week's spreadsheet.

If you're setting your split now, we offer a free inventory allocation review. Send us your recent and last-Q4 order data, and we'll map where your peak stock should go.

See also: inventory management for 3PL-managed brands, health and supplement fulfillment, and the BFCM order automation playbook.