What is available-to-promise (ATP)?

Published

October 22, 2026

Last updated

October 22, 2026

Definition

Available-to-promise (ATP) is the quantity of inventory that isn't committed to existing customer orders, which a business can promise to new orders for a given date. Planners calculate ATP across time buckets, so they know both how much they can promise and when.

ATP connects supply planning to sales commitments. Pull-based ATP subtracts confirmed orders from on-hand stock, while push-based ATP starts from beginning inventory plus planned supply. ERP systems run ATP checks in real time for each order or in batch to confirm delivery dates the business can meet.

Reliable dates protect revenue across the order-to-cash cycle and keep teams from holding extra stock to cover uncertain promises, which ties up working capital. ATP only counts inventory and scheduled supply. Whether the business can make more is a question for capacity planning and capable-to-promise (CTP).

Related terms

Supply Planning

Capacity Planning

Order to Cash

Integrated Business Planning (IBP)

Frequently Asked Questions

How is ATP calculated?

ATP equals on-hand inventory plus scheduled receipts minus committed customer orders for each time period. Discrete ATP calculates each period on its own, while cumulative ATP carries unused quantities forward into later periods.

How does ATP differ from capable-to-promise (CTP)?

ATP only considers existing inventory and scheduled receipts. Capable-to-promise (CTP) also checks production capacity, supplier lead times, and materials to confirm whether the business can make or source more.

How is ATP different from on-hand inventory or safety stock?

On-hand inventory is the stock physically in the warehouse, and safety stock is a buffer held against demand or supply variability. ATP is the uncommitted quantity you can still promise, so it can change daily and go negative when commitments exceed supply.