What the stock numbers mean

The nine stock figures, from on hand to available, short, on order and drop ship: what each counts, the arithmetic between them, and where the same numbers show.

Every screen that shows a quantity of stock reads the same nine figures, worked out one way for every item at every place: the item page, Inventory, Stock, pick tickets, purchasing, the retail add-on's restocking, the material plan, the online store's "in stock" and "sold out", the assistants and the API. When two screens show a number for the same item, they agree, and this page says what each number counts.

The nine figures

On hand: every unit counted at the place, whatever state it is in. It is the sum of the stock tags there. For the business as a whole, stock on its way between your own locations is on hand too.
Not available: on hand that cannot be sold or used. Stock at a place that is held (a quarantine shelf, damaged goods, returns waiting on an inspection), a lot or a delivery on hold for quality (waiting on its inspection, failed, or held by hand; see Quality), lots past their expiration date, stock on its way between locations, and stock a customer holds on consignment.
Allocated: on an open pick ticket at the place and not yet picked. A picker is on the way to it, or will be.
Committed: promised to something that is not on a pick ticket yet: an open store, wholesale or marketplace order, a client's order (fulfillment), a transfer not yet shipped, a production run's materials (what is still to send, and what was sent to the maker and not yet used), or a consignment transfer. An order that does not yet say where it ships from is counted at the place the business ships from (see below).
Available: what can be promised to something new. Available = On hand − Not available − Allocated − Committed. Below zero means more is promised than is there.
Short: how much of what is promised the place cannot cover. Short = Allocated + Committed − (On hand − Not available), when that is more than zero; otherwise 0.
On order: coming in and not yet received: open purchase orders delivered to the place's location (drafted or ordered), transfers shipped toward it, and production runs due to deliver finished goods there. Asked for a day (the API's asOf), only what is expected by that day counts, and what names no day counts too. For the business as a whole, transfers between your own locations are your stock already, so they are not on order.
Available to pick: of what is allocated, what is really on a stock tag at the place in a bin orders are picked from. It is less than allocated when a ticket was short from the start.
Drop ship: always 0. Nothing is drop-shipped through the app; every unit you sell passes through a place of your own. The figure is here so nobody wonders.

Each document is counted once

An order on an open pick ticket is allocated, not committed as well. A transfer on a ticket is allocated; one not yet on a ticket is committed at the place it leaves from. A production run's materials already on a transfer to the plant are the transfer's, not the run's. Two pick tickets can never promise the same unit: a second ticket made at a place is short by what the first already holds.

Where an order is counted before it ships

A store, wholesale or marketplace order does not say which shelf it ships from until it is picked or shipped. Until then it is counted at the business's home place: the place the online store ships from when Online Store, Shipping names one; else the place parcels go out from under Shipping, Settings; else the first place orders are picked from. A purchase order that names no location is expected at your first plant when you have one (as the material plan reads it), else at the home place. The item page's Availability card says which place that is.

Where the numbers show

Inventory, Parts, an item, Stock: the Availability card shows the nine figures for the business as a whole, each with its sentence when you tap it; the same nine at each place under its location; and Why?, which lists the orders, tickets, transfers, runs and purchase orders behind what is allocated, committed and on order, each opening where it lives.
Inventory, Stock, Every location: Available and On order beside On hand. Figures chooses which of the nine show as columns.
Purchasing, Worksheet: each row reads available and on order, so a shelf on hold or past its date no longer counts as stock, and each item's Forecast starts from on hand less not available. See Purchasing: what to order and when.
Pick tickets: a ticket is made from what is available to the place, counting the open tickets already there, and says what is short from the start.
Retail restocking and the manufacturing Materials plan read the same figures for the place they work from.
The online store's Sold out and Only n left read the item's available at the place the store ships from (else the business as a whole).
The assistant answers "how many do we have" with available, and says on hand only when asked.
The API: GET /inventory/availability, GET /inventory/availability/{id} (with the documents behind each figure), and every inventory item carries available, onOrder and the nine figures.

Best practices

Hold a shelf (Inventory, Setup, the place's rules, or Losses, hold the tags) rather than counting damaged stock down: it stays on hand and shows as not available, so the value is still on the books until you write it off.
Set the place the store ships from under Online Store, Shipping, so the store's figures are that place's and an order is counted where it will leave from.
When available is below zero, open Why? on the item: it names the orders and transfers to decide between, and the purchase orders already on the way.