Inventory planning
Available to Promise (ATP)
By the Supply Chain Manager team · Updated October 16, 2026
Available to promise (ATP) is the quantity you can commit to a new order by a given date, after current stock, incoming supply and existing commitments.
ATP looks forward in time. It starts from available stock, adds scheduled receipts such as open purchase orders, and subtracts orders already promised, period by period. It answers the sales question 'how many can I promise, and by when?'.
Many businesses calculate ATP only for items that are short or have large orders pending, because for well-stocked items the answer is simply 'yes, today'. Where it matters most is for scarce stock: allocating limited supply across customers by agreed priority instead of first come, first served.
How to calculate ATP
ATP (period) = Available stock + Scheduled receipts − Committed customer orders, through that period
ATP example
Illustrative numbers: 100 available today, 300 arriving next week, 250 already promised for next week. You can promise 100 today and only 150 more for next week, not 400.
Why ATP matters for distributors
Promising accurate dates keeps wholesale customers planning around you rather than around a competitor. ATP turns 'let me check with purchasing' into an immediate answer.
Common ATP mistakes
- Promising against incoming stock with an unreliable supplier date.
- Calculating ATP once a day while orders keep coming in.
Examples on this page use made-up round numbers to show the calculation. They are not benchmarks or results from real businesses.