Calcul Available To Promise

Use this premium ATP calculator to estimate how much inventory you can still commit to customers after accounting for on hand stock, inbound receipts, planned production, confirmed orders, and optional safety stock protection.

Available to Promise is one of the most practical metrics in operations, supply chain, and order management because it answers a simple but critical question: how much can we promise right now without creating avoidable stockouts?

What is calcul available to promise?

Calcul available to promise, commonly called ATP calculation, is the process of determining how much inventory or future production can still be committed to customers without putting service levels at risk. In practical terms, ATP tells a business whether it can accept a new order and when that order can realistically be fulfilled. The concept sits at the center of supply chain planning, demand management, inventory control, and customer service because it connects operational reality with commercial promises.

When an order management team says, “Yes, we can ship 300 units next week,” that statement should not be based on guesswork. It should be based on inventory currently on hand, inbound receipts, scheduled production, already allocated orders, and in many cases a protected safety stock level. ATP helps organizations turn all of those inputs into a reliable answer.

Although ATP can be very sophisticated inside enterprise resource planning systems, the basic logic is straightforward. You start with supply, subtract demand already committed, and account for any reserve you are not willing to consume. The result is the quantity that remains available to promise.

Core ATP formula

For a simplified operational estimate, a widely used formula is:

Gross ATP = On hand inventory + Scheduled receipts + Planned production – Committed customer orders
Net ATP = Gross ATP – Safety stock

This approach is especially useful for quick planning reviews, sales and operations conversations, and order acceptance decisions when you need a clear answer immediately. More advanced systems may calculate ATP by time bucket, by SKU, by site, by channel, or by customer priority.

Why available to promise matters in real operations

ATP matters because customer commitments are expensive to break. A weak promise process leads to backorders, expediting costs, excess overtime, avoidable air freight, and lower trust across the supply chain. On the other hand, a disciplined ATP process can improve customer satisfaction while reducing firefighting in production and logistics.

• Sales teams use ATP to commit realistic dates and quantities.
• Customer service teams use ATP to answer order status questions quickly and accurately.
• Planners use ATP to balance demand with finite supply.
• Warehouse teams benefit because ATP reduces surprise allocation changes.
• Executives benefit through better service levels, lower premium freight, and cleaner revenue forecasting.

In sectors with volatile demand, long lead times, or high service expectations, ATP has an even stronger impact. Manufacturers, distributors, wholesalers, healthcare suppliers, consumer packaged goods brands, and ecommerce operations all depend on some form of ATP logic to align order commitments with reality.

Understanding the major ATP inputs

1. On hand inventory

This is the quantity physically available right now. It should ideally reflect inventory accuracy after reservations, quality holds, and unusable stock are excluded. If on hand inventory is overstated, ATP will also be overstated.

2. Scheduled receipts

Scheduled receipts are inbound shipments or production orders that are already confirmed and expected within the relevant promise window. These receipts can include supplier deliveries, transfer orders from another facility, or work orders finishing soon.

3. Planned production or MPS receipt

In many manufacturing environments, ATP depends heavily on the master production schedule. If a production run is due within the order commitment horizon, it can increase ATP. However, planners should only include realistic, capacity checked, and material feasible quantities.

4. Committed customer orders

These are orders already promised to customers. ATP is not just a supply measure. It is a netting process that subtracts what has already been committed. The higher the backlog, the lower the remaining ATP.

5. Safety stock

Safety stock is a deliberate buffer held to absorb variability in demand or supply. Many organizations prefer to calculate net ATP by protecting that reserve. Doing so creates a more conservative, service oriented promise number.

Gross ATP versus net ATP

One of the most important distinctions in ATP calculation is whether safety stock is included or protected. Gross ATP is more aggressive because it assumes all supply can be used to satisfy orders. Net ATP is more conservative because it treats safety stock as untouchable in normal planning.

Metric	Formula logic	Best use case	Risk profile
Gross ATP	Supply minus committed orders	Fast commercial screening when service buffers are flexible	Higher risk of stockouts if variability rises
Net ATP	Supply minus committed orders minus safety stock	Service sensitive environments and unstable lead times	Lower risk and generally more reliable commitments

If your operation experiences frequent supplier disruption, demand spikes, or inventory accuracy issues, net ATP is usually the wiser choice. If your supply is very stable and the cost of conservatism is high, gross ATP may be acceptable in narrow situations. Many mature companies use both views: gross ATP for internal visibility and net ATP for external customer commitments.

Worked ATP example

Imagine a distributor with the following numbers for a single SKU over the next 14 days:

• On hand inventory: 1,200 units
• Scheduled receipts: 450 units
• Planned production or transfer: 800 units
• Committed orders: 1,700 units
• Safety stock: 150 units

The calculation would be:

1. Total supply = 1,200 + 450 + 800 = 2,450 units
2. Gross ATP = 2,450 – 1,700 = 750 units
3. Net ATP = 750 – 150 = 600 units

In this example, the company can still promise 600 units if it intends to preserve its safety stock. If it ignores safety stock, it could technically promise 750 units, but that would leave less protection against variability.

Operational statistics that support ATP discipline

Available to Promise is closely tied to service performance, order cycle consistency, and inventory health. The numbers below summarize selected public indicators from authoritative sources often used in operations analysis. These statistics do not define ATP by themselves, but they explain why disciplined promise logic matters.

Indicator	Recent public figure	Source	Why it matters for ATP
Manufacturing share of U.S. GDP	About 10% to 11%	U.S. Bureau of Economic Analysis	Large economic exposure means promise accuracy affects a major base of industrial activity.
Average manufacturing capacity utilization	Often near 75% to 80% depending on period	Federal Reserve industrial production data	When utilization is tight, ATP assumptions must reflect finite production capacity.
Inventory to sales ratios in wholesale and retail sectors	Commonly near 1.1 to 1.4 in many periods	U.S. Census economic indicators	Inventory positioning directly shapes how much can be promised without delay.

These ranges shift over time, but the pattern is consistent: operational volatility, finite capacity, and changing inventory positions all affect how trustworthy a promise quantity can be. ATP is the mechanism that turns those conditions into an actionable commitment rule.

Common mistakes in ATP calculation

Counting supply that is not truly available

A frequent error is including stock that is damaged, on hold, reserved for a strategic customer, or physically present but not pickable. ATP quality depends on inventory quality.

Ignoring timing

Supply arriving after the requested ship date should not support an immediate promise. Time phased ATP is more accurate than a simple aggregated view, especially for high volume operations.

Overlooking order priorities

Not all customer orders have equal strategic value. Some organizations reserve ATP for premium channels, contracted customers, or medically critical products.

Using stale receipts or unrealistic production plans

If inbound receipts are delayed or a planned order is not material feasible, ATP must be revised. Static assumptions create false confidence.

Failing to protect safety stock

When supply uncertainty is high, promising inventory down to zero may create immediate service failures. Safety stock should exist for a reason, and ATP should respect that reason.

How ATP differs from related inventory metrics

ATP is often confused with inventory available, projected available balance, or capable to promise. The differences matter:

• Inventory available usually means stock physically available now.
• Projected available balance looks ahead by time period and tracks expected balances after demand and receipts.
• Available to Promise focuses on what can still be committed to new demand.
• Capable to Promise goes further by considering whether capacity and materials can be reconfigured to meet custom demand.

In short, ATP is promise focused rather than merely stock focused. It is meant to support a customer commitment decision.

Best practices for improving ATP accuracy

1. Improve inventory accuracy. Cycle counting, barcode discipline, and clearer status controls reduce ATP errors.
2. Refresh supply data frequently. Late supplier confirmations or delayed work orders can change ATP fast.
3. Use realistic lead times. Standard lead times should be audited against actual performance.
4. Segment products. Fast movers, seasonal SKUs, and strategic items often need different ATP logic.
5. Protect critical service buffers. Safety stock and reserved allocations should be explicit, not assumed.
6. Align sales and operations. ATP rules work best when planners and commercial teams use the same logic.
7. Track promise adherence. Measure whether promised orders shipped in full and on time.

When to use this calculator

This calculator is ideal when you need a clear single period ATP estimate for a product, lane, or inventory node. It is helpful in these situations:

• Quick order acceptance checks
• Sales and operations planning meetings
• Distributor replenishment reviews
• Production scheduling conversations
• Backorder recovery planning
• Scenario analysis before changing safety stock policy

For a full enterprise environment, ATP may also need to consider lot control, expiration constraints, multi warehouse sourcing, customer allocation rules, transportation capacity, and substitution logic. Still, a disciplined base formula like the one above remains the foundation.

Authoritative references for deeper reading

If you want to connect ATP concepts with broader production, inventory, and economic planning data, these authoritative sources are useful:

• U.S. Bureau of Economic Analysis for production and industry contribution data.
• Federal Reserve Industrial Production and Capacity Utilization for capacity context that affects realistic promises.
• U.S. Census Bureau Economic Indicators for inventory, shipments, and sales trends relevant to supply planning.

Final takeaway

Calcul available to promise is not just a formula. It is a practical discipline for protecting customer trust and operational stability. Every promise has a cost if it is wrong, and every conservative holdback has a cost if it is too cautious. Good ATP logic helps organizations find the right balance. By combining on hand inventory, inbound supply, production plans, committed demand, and safety stock policy, businesses can make commitments with far greater confidence.

Use the calculator above whenever you need a fast ATP estimate. For the most reliable results, keep your data current, validate your inventory accuracy, and make sure your planned receipts are truly achievable within the promise window.