What Is Available to Promise (ATP) in Manufacturing?

Available to promise, usually abbreviated ATP, is the quantity of a product you can honestly commit to a new customer without breaking a promise you have already made. It is not the same as stock on hand and it is not the same as projected balance. ATP starts from the physical inventory you have now, adds the supply scheduled to arrive, subtracts every firm order already committed against that supply, and reports what is left to sell.

This entry defines ATP and shows how it behaves inside EDGEBIC by User Solutions. For the wider index of planning terms, see the manufacturing glossary, and for the balance figure that sits beside ATP on the same calendar, see projected available balance. A generic definition also lives in the ATP glossary entry; this entry takes the planner-facing view of how the figure is computed and read.

How it works

The cleanest way to picture available to promise is a restaurant on a busy night. The host does not say "we theoretically seat 50." The host says "we have three tables left tonight, I can promise you one." Fifty is the physical capacity; three is what is genuinely free after the reservations already taken. ATP is that same distinction applied to inventory: what is uncommitted, not what exists.

The calculation is forward-looking and anchored to physical on-hand now, not to a historical opening balance. It also has an outer edge, the ATP horizon, past which there are no buckets and so no calculated promise. It produces two values per time bucket:

• Discrete ATP is the promise capacity created at one supply point. At each point it takes the supply arriving there and subtracts all firm demand up to the next supply event.
• Cumulative ATP is the running total of those discrete figures, carried forward across supply points so that even non-supply buckets show an updated promise position.

Two behaviors matter for using ATP correctly. First, quote from the cumulative column, because a customer asking "how many by this date?" wants the total, not the slice created at one supply point. Second, negative values are real and shown, not suppressed. A negative figure is the earliest and clearest signal that commitments have run ahead of supply.

A concrete example

A product opens with 120 units physically on hand. One build-to-stock order for 150 units is scheduled to complete in week two. Firm orders total 50 in week one and 20 in week two.

At the first supply point (week one, carrying the 120 on hand): supply is 120, firm demand up to the next supply event is 50, so discrete ATP is 120 minus 50, or 70. Cumulative starts at 70.

At the second supply point (week two, the 150-unit receipt): supply is 150, firm demand from here to the end is 20, so discrete ATP is 150 minus 20, or 130. Cumulative becomes 70 plus 130, or 200.

The planner can promise up to 70 more units before the week-two build lands, and up to 200 more in total across the horizon. If firm demand had instead been 250 in week one, discrete ATP would read minus 130, flagging that the shop has already sold more than it has, which is a promise problem to solve now rather than discover at ship time.

How EDGEBIC uses it

In EDGEBIC, available to promise is computed alongside projected available balance in the Inventory Calendar, using physical on-hand from the inventory ledger as the promise starting point. Each row carries both a discrete and a cumulative ATP figure, and negative values are shown rather than clamped, so an oversell surfaces the moment it appears in the plan.

Because ATP is a materials answer, a promise worth making pairs it with a timing answer. ATP confirms that uncommitted units exist or are scheduled to arrive; it says nothing about whether a machine is free to run the job on time. EDGEBIC's quote simulation provides the timing side by running the prospective order against the finite-capacity schedule, so a planner can promise a date backed by both material and capacity.

For the full computation with discrete and cumulative worked through, read available to promise in EDGEBIC. To understand the demand figures that ATP subtracts, continue with firm demand in planning and forecast consumption.