How do you calculate available to promise?

Subtract firm sales order allocations, protected safety stock, and any quality-held or blocked stock from your available supply. With 1,800 units of supply, 940 allocated, 250 safety stock, and 80 on quality hold, ATP is 1,800 - 940 - 250 - 80 = 530 units.

What is the difference between ATP and on-hand inventory?

On-hand is everything physically in the building. ATP is only the slice you can still sell: it strips out units already committed to firm orders, the safety-stock cushion you protect, and anything blocked by quality. In the example, 1,800 on-hand becomes just 530 promisable.

Should safety stock be subtracted from ATP?

Yes, if you treat safety stock as protected. Most disciplined planners do, because promising into the safety buffer defeats its purpose. Here the 250-unit buffer is deducted, which is why 1,270 units (29.4% of supply) are committed, protected, or blocked and only 530 remain promisable.

What is a good ATP number?

There is no universal target; ATP is healthy when it stays positive and tracks your forecasted incoming demand. A persistently negative ATP signals over-commitment or short receipts; a very large ATP can mean excess stock or weak demand. Trend it by item rather than chasing an absolute value.

How often should ATP be recalculated?

Recheck it whenever receipts post, allocations change, or quality status flips. ATP is only valid for the instant it was computed, so order-promising systems typically recalculate it in real time on each new order line.

What is the difference between ATP and CTP (capable to promise)?

ATP looks only at existing and scheduled supply. CTP goes further and asks whether you could build more in time using available capacity and materials. Use ATP for quick confirmations against stock; use CTP when you need to promise beyond current supply.

ERP & MRP Planning calculator

Available to Promise Calculator

Available to Promise (ATP) is the uncommitted portion of inventory and scheduled receipts that a planner or order-desk rep can safely pledge to a new customer order without breaking existing commitments. Master schedulers, customer service teams, and ERP/MRP planners check ATP before they confirm a delivery date so they don't double-promise the same stock. It matters because an over-promised line generates a broken delivery, an expedite, or a stockout the moment the firm orders behind it pull their inventory. Getting ATP right is the difference between a clean confirmation and a credibility-killing slip date.

What this calculator does

Estimate available-to-promise quantity after firm sales allocations, safety stock, and quality holds.
a planner needs to know how many units can still be promised to new demand
It computes the net quantity you can still promise after subtracting firm order allocations, protected safety stock, and any quality-held or blocked inventory from available supply.

Formula used

Available to promise = available supply - firm allocations - protected safety stock - quality hold or blocked stock
ATP should be checked again if receipts, allocations, or quality status change.

Inputs explained

Available supply before new order:
Firm sales order allocations:
Protected safety stock:
Quality hold or blocked stock:

How to use the result

Use it at the order-promising step, every time receipts, allocations, or quality status change, before you confirm a ship date to a customer.
It is a static snapshot of one item at one moment; it ignores in-transit receipts not yet posted and does not net across substitute SKUs or future MRP supply unless you fold those into the supply figure yourself.

Current U.S. benchmarks

Manufacturing hourly earnings average $30.27 (BLS, Jun 2026), up 4.4% from a year earlier. Median machinist pay is $28.24/hr (OEWS 2025), with state medians on each state page. Manufacturers have 529k open positions nationally (BLS JOLTS).
U.S. manufacturing runs at 75.6% of capacity (Federal Reserve, May 2026). New factory orders are up 2.3% year over year (Census).

Common questions

How do you calculate available to promise? Subtract firm sales order allocations, protected safety stock, and any quality-held or blocked stock from your available supply. With 1,800 units of supply, 940 allocated, 250 safety stock, and 80 on quality hold, ATP is 1,800 - 940 - 250 - 80 = 530 units.
What is the difference between ATP and on-hand inventory? On-hand is everything physically in the building. ATP is only the slice you can still sell: it strips out units already committed to firm orders, the safety-stock cushion you protect, and anything blocked by quality. In the example, 1,800 on-hand becomes just 530 promisable.
Should safety stock be subtracted from ATP? Yes, if you treat safety stock as protected. Most disciplined planners do, because promising into the safety buffer defeats its purpose. Here the 250-unit buffer is deducted, which is why 1,270 units (29.4% of supply) are committed, protected, or blocked and only 530 remain promisable.
What is a good ATP number? There is no universal target; ATP is healthy when it stays positive and tracks your forecasted incoming demand. A persistently negative ATP signals over-commitment or short receipts; a very large ATP can mean excess stock or weak demand. Trend it by item rather than chasing an absolute value.
How often should ATP be recalculated? Recheck it whenever receipts post, allocations change, or quality status flips. ATP is only valid for the instant it was computed, so order-promising systems typically recalculate it in real time on each new order line.

Last reviewed 2026-05-12.