On-hand, reserved, available: the three numbers behind every oversell

Ask a warehouse "how many of these do we have?" and you'll get a number. The problem is that there are at least three right answers, and picking the wrong one is how you end up selling stock you can't ship.

The three numbers

On-hand is what's physically on the shelf. If you walked the aisle and counted, this is the number you'd get. It's real, it's tangible, and on its own it's misleading — because some of it is already spoken for.

Reserved (or allocated) is the portion of on-hand that's been promised to orders already in the pipeline. The units are still on the shelf, but they're not yours to sell again. In Bonsai WMS this is tracked per inventory record as an allocated quantity, with a hard rule that you can never allocate more than you physically hold.

Available is the number that actually matters for selling:

available = on-hand − reserved

It's what you can safely promise to the next customer. Publish on-hand to your sales channels instead of available, and you will oversell the moment two orders chase the same units.

Why "available" can't be a guess

The trap is treating availability as something you compute occasionally — an overnight job, a spreadsheet someone refreshes. Demand doesn't wait for the batch. An order placed at 10:02 reserves stock that an order at 10:03 must not be able to claim.

That's why availability has to fall out of the system in real time, as a consequence of the same transaction that creates the allocation — not a number that's reconciled after the fact. Every allocation moves a unit from available to reserved atomically. There's no window where two orders both see it as free.

Location makes it harder (and better)

It gets more interesting once stock lives in specific places. The same SKU might sit in three bins across two warehouses. "Available" isn't just a single global figure; it's a question you can ask per location, per warehouse, or across the whole operation.

Bonsai tracks inventory down to the individual location, so the system can answer "available to this pick path, from this zone" — not just "available somewhere, eventually." That's what lets picking stay efficient without lying to the storefront.

The takeaway

If your inventory tooling shows you one number, be suspicious. The useful answer to "how many do we have?" is almost always three numbers — and the one you put in front of customers should be available, computed live, every time.