Available to Promise (ATP)
The uncommitted portion of a company inventory that can be promised to new customer orders based on current stock minus reservations.
Available to Promise (ATP) is the uncommitted portion of a company's inventory that can be promised to new customer orders based on current stock minus reservations. ATP calculates what's truly available for sale by subtracting existing customer commitments, backorders, and reserved stock from on-hand inventory and planned production. This real-time metric helps businesses make accurate delivery promises while preventing overselling and maintaining customer trust.
Why it matters for e-commerce brands
For online retailers, ATP is critical to avoiding the costly mistake of promising products you can't actually deliver. When you sell across multiple channels—your Shopify store, Amazon, wholesale partners—ATP ensures you're not double-promising the same inventory, which leads to cancelled orders, disappointed customers, and damaged brand reputation. Accurate ATP calculations enable you to display realistic stock availability, set appropriate delivery dates, and maintain high fulfillment rates even during peak demand periods.
Example
A Shopify store selling yoga mats has 100 units in their warehouse. They have 30 units allocated to existing orders awaiting shipment, 15 units reserved for a wholesale customer order shipping next week, and 10 units set aside as safety stock. Their ATP is 45 units (100 - 30 - 15 - 10 = 45). When a customer visits their product page, the inventory system can confidently show "45 available" and accept new orders up to that quantity. If the brand expects a shipment of 200 units arriving in two weeks, they might also display a future ATP that accounts for this incoming inventory, allowing customers to pre-order with accurate delivery expectations.
Related terms
- Capable to Promise (CTP): Future inventory availability including planned production and scheduled receipts
- Safety Stock: Reserve inventory kept to prevent stockouts from unexpected demand or supply delays
- Allocated Inventory: Stock reserved for specific customer orders or purposes that cannot be sold
- Lead Time: The time required between ordering and receiving inventory
- Inventory Visibility: Real-time tracking of stock levels across all locations and channels
Put Available to Promise (ATP) knowledge into practice
Forthsuite's tools are built around exactly these concepts — giving Shopify merchants the data and automation to manage their supply chain with confidence.