A customer wants 1,000 units. Your company can supply only 700.
So what is the demand: 700 or 1,000?
That sounds like a small distinction, but it can change how a company forecasts sales, plans production, manages inventory, and decides whether it needs more capacity.
The 1,000 units represent what customers want if the supply limitation isn’t holding them back. The 700 units represent what the business can realistically support under its current limitations.
This is the basic idea behind unconstrained demand vs. constrained demand.
The distinction becomes especially important in demand planning and Sales and Operations Planning (S&OP), where sales, supply chain, manufacturing, finance, and operations need to agree on what the business expects to sell and what it can actually deliver. SAP, for example, recommends keeping the unconstrained demand view visible before supply constraints are applied, rather than allowing current capacity limitations to quietly become the forecast.
What Is Unconstrained Demand?
Unconstrained demand is the amount of product or service customers are expected to want without reducing that demand because of current supply limitations.
In other words, it answers:
“How much would customers buy if we had enough product available?”
The estimate can take into account things such as:
- historical demand
- customer orders and expectations
- market trends
- promotions
- new product launches
- pricing changes
- sales-team knowledge
- competitive activity
- seasonal patterns
What it does not do is automatically lower the forecast simply because the business currently lacks enough inventory, production capacity, labor, or materials.
This makes unconstrained demand useful for understanding the opportunity that exists in the market.
For example, a manufacturer may expect demand for 15,000 units next month. Its factory, however, can currently produce only 10,000.
The unconstrained demand is still 15,000.
The production limitation doesn’t make those additional 5,000 units disappear. It means the company currently doesn’t have the ability to satisfy all of that demand.
What Is Constrained Demand?
Constrained demand takes supply limitations into account when determining what can realistically be fulfilled.
Those limitations can come from almost anywhere in the supply chain.
For example:
- production capacity may be limited
- raw materials may be unavailable
- inventory may be too low
- a supplier may have a long lead time
- labor may be insufficient
- transportation capacity may be restricted
- warehouse capacity may be limited
- a particular production line may be unavailable
So, if customers want 15,000 units but the business can realistically supply 10,000, the constrained plan needs to reflect that limitation.
That’s why constrained demand is closely connected to supply planning and execution.
Constrained vs Unconstrained Demand at a Glance
| Unconstrained Demand | Constrained Demand | |
|---|---|---|
| Basic question | What do customers want? | What can we realistically fulfill? |
| Supply limitations | Not used to reduce the initial demand view | Taken into account |
| Main purpose | Understand market demand and opportunity | Build an achievable operating plan |
| Common use | Demand planning, forecasting, S&OP | Supply planning, production, allocation |
| Helps with | Growth and capacity decisions | Execution and fulfillment |
| Main risk | May exceed available supply | May hide unmet demand if used alone |
The important thing is that neither number is automatically “the right one.” They are useful for different decisions.
A Simple Example
Imagine a company sells commercial refrigerators.
Its sales team expects customers to need 5,000 refrigerators next quarter.
But the company has a problem.
One of its suppliers can’t provide enough compressors, so production can support only 3,500 refrigerators.
The planning picture now looks like this:
Unconstrained demand: 5,000
Available production capability: 3,500
Potential demand not currently fulfilled: 1,500
If the company records only 3,500 as its demand forecast, management might conclude that the market needs roughly 3,500 refrigerators.
But that’s not necessarily true.
The company may simply be unable to supply the remaining 1,500.
That difference matters because management may need to ask a completely different question:
“How do we remove the constraint?”
Perhaps the answer is another supplier, additional production capacity, overtime, alternative materials, or a change in sourcing.
Why Unconstrained Demand Matters
One of the biggest problems in demand planning is confusing what the company sold with what customers wanted.
Suppose a business has enough inventory to sell 800 units.
Customers actually want 1,100.
The company sells all 800.
Looking at the sales report, someone might say:
“We sold 800, so demand was 800.”
But that’s only part of the story.
There may have been another 300 units of demand that the business couldn’t satisfy.
If planners repeatedly use the 800-unit figure as the future forecast, the business can end up planning around its existing limitation rather than the market opportunity.
SAP describes this as a potential danger of forecasting only constrained demand: if the constraint becomes part of the forecast, the organization can create a cycle in which limited supply leads to a lower forecast, which then provides little pressure to remove the supply limitation.
Why Constrained Demand Matters
That doesn’t mean constrained demand is unimportant.
Quite the opposite.
A business can’t manufacture, purchase, store, or ship an unlimited amount of product simply because customers want it.
At some point, someone has to answer:
“Given the resources we actually have, what can we deliver?”
That’s where the constrained view becomes useful.
It can help teams make decisions about:
- production schedules
- inventory allocation
- procurement
- supplier capacity
- customer commitments
- warehouse operations
- transportation
- service levels
- available capacity
SAP’s S&OP planning materials describe the supply review as the stage where anticipated demand is compared with current or projected supply, helping planners identify gaps between what is needed and what the supply chain can support.
The Biggest Mistake: Treating Constraints as Demand
This is where the difference becomes especially important.
Imagine your factory can make 10,000 units a month.
For several months, customers want around 14,000.
You keep producing 10,000 and selling 10,000.
After a while, someone looks at the historical sales and says:
“Our monthly demand is about 10,000.”
But maybe it isn’t.
Maybe 10,000 is simply the maximum the factory has been able to supply.
That is a very different situation.
If the company believes 10,000 is the true market demand, it may never investigate whether expanding capacity could generate another 4,000 units in sales.
This is why keeping the unconstrained demand signal visible can be valuable.
Demand Is Not Always the Same as Sales
This distinction is easy to overlook.
Sales are based on transactions that actually happened.
Demand is about what customers wanted or were expected to want.
Under normal conditions, the two can be fairly close.
Under supply shortages, they can move apart.
For example:
A customer requests 500 units.
The supplier confirms 350.
The customer receives 350.
If you look only at shipments, you see 350.
But the original requirement was 500.
The difference may become:
- a backorder
- a delayed shipment
- a lost sale
- a substitute purchase
- a cancelled order
The exact outcome depends on the customer and the situation, but the key point remains: fulfilled quantity doesn’t always reveal the full level of demand.
This is one reason demand planners need to be careful when historical sales have been affected by stockouts or other supply constraints.
What Causes Demand to Become Constrained?
There isn’t just one type of constraint.
1. Production Capacity
A factory may receive more demand than its machines can handle.
For example, customers want 20,000 units, but available production capacity is 15,000.
2. Inventory Shortage
The company may have enough production capacity but not enough finished goods available for immediate delivery.
3. Raw-Material Shortage
A single missing component can stop production even when demand is strong.
A manufacturer might have orders for 10,000 finished products but enough components to build only 7,000.
4. Supplier Constraints
A supplier may have its own capacity limitations, long lead times, or allocation rules.
That limitation can then move downstream through the supply chain.
5. Labor Constraints
A company may have equipment available but not enough workers to operate it.
6. Transportation Constraints
A business may have the products ready but lack sufficient trucks, containers, drivers, or transportation capacity.
7. Warehouse Constraints
Storage or handling capacity can also become a bottleneck.
The result is the same basic problem: the market may want more than the supply chain can currently support.
How the Two Views Work Together in S&OP
The distinction between constrained and unconstrained demand becomes particularly useful in Sales and Operations Planning (S&OP).
A simplified process looks like this:
Market demand → Unconstrained demand plan → Supply review → Constraints identified → Realistic supply/constrained plan → Management decisions
The demand side first asks:
What do we expect customers to want?
The supply side then asks:
What can we actually provide?
The gap between those two answers is often where the most important business decisions are found.
For example:
- Do we need more capacity?
- Should we increase inventory?
- Do we need another supplier?
- Should we prioritize certain customers?
- Is the demand opportunity large enough to justify investment?
- Are some constraints temporary or structural?
SAP’s S&OP guidance describes demand review and supply review as distinct parts of the planning process, with both constrained and unconstrained views helping teams understand whether projected supply can meet anticipated demand.
Should You Forecast Constrained or Unconstrained Demand?
For the initial demand forecast, an unconstrained view is generally more useful.
The reason is simple: the forecast should tell the business what the market is likely to require, rather than simply repeating what the current supply chain can produce.
SAP has long recommended using unconstrained demand in the forecasting process and applying supply constraints later during S&OP.
But that doesn’t mean you should ignore constraints.
A useful planning process keeps both questions visible:
Demand question:
How much are customers likely to want?
Supply question:
How much can we realistically deliver?
You need both answers before making a serious business decision.
What Happens When You Use Only Constrained Demand?
Using only constrained demand can create a misleading picture.
Imagine your market could support 50,000 units a year, but your current production capacity is 35,000.
If your forecast is automatically reduced to 35,000 every year, your planning system may never clearly show that 15,000 units of potential demand are being left on the table.
This can affect decisions about:
- factory expansion
- equipment purchases
- staffing
- supplier development
- inventory investment
- sales targets
- revenue planning
The business may effectively plan for today’s limitations instead of asking whether those limitations should change.
What Happens If You Use Only Unconstrained Demand?
There is a problem at the other extreme too.
Suppose the unconstrained forecast says customers will want 100,000 units.
But the business has capacity for only 60,000.
If the company simply tells production, procurement, and logistics to prepare for 100,000 without addressing the gap, the plan isn’t realistic.
It could result in:
- shortages
- missed delivery dates
- unrealistic customer commitments
- excessive overtime
- procurement pressure
- poor service levels
So unconstrained demand shouldn’t be treated as a promise that the business can automatically fulfill it.
It is a demand signal and planning view, not a guarantee of available supply.
The Better Approach: Keep Both Views Visible
The strongest approach isn’t really constrained vs. unconstrained.
It’s constrained and unconstrained.
Think of them as two lenses looking at the same business.
The unconstrained view shows the opportunity.
The constrained view shows the reality of the current supply chain.
Put them together and management can see the gap.
For example:
| Planning View | Quantity |
|---|---|
| Expected customer demand | 12,000 |
| Available supply | 8,500 |
| Gap | 3,500 |
Now the conversation becomes much more useful.
Instead of saying:
“Our forecast is 8,500.”
the team can say:
“Demand is expected to be 12,000, but our current supply plan supports only 8,500. We need to decide what to do about the 3,500-unit gap.”
That’s a much clearer basis for an S&OP discussion.
How Do You Estimate Unconstrained Demand?
This becomes difficult when historical data has already been affected by shortages.
Suppose a product was out of stock for three weeks last year.
Its recorded sales during that period may be much lower than the demand that would have occurred if the product had been available.
A planner may therefore need to look beyond sales history and examine things such as:
- unfulfilled orders
- backorders
- stockout periods
- cancelled orders
- customer requests
- lost-sales information
- substitution behavior
- market trends
- promotional activity
- sales-team input
- capacity restrictions
The purpose isn’t to invent demand.
It’s to avoid treating a supply problem as if it were a genuine lack of customer interest.
In demand forecasting research, this broader problem is often described as demand unconstraining: estimating the demand that would have been observed if a particular restriction had not prevented customers from buying.
A Real-Life Analogy
Think about a small restaurant that sells its most popular pizza.
On Friday night, 100 customers want it.
The kitchen can make only 60.
By 9 p.m., all 60 have been sold.
If you look at the sales report, you see 60 pizzas.
But did the restaurant have demand for only 60?
Probably not.
The remaining customers couldn’t buy the pizza because the kitchen had reached its limit.
If the restaurant owner is planning next Friday based only on the 60 pizzas sold, the same shortage could happen again.
The better question is:
“How many people wanted the pizza, and how many could we actually serve?”
That’s essentially the same question supply-chain planners are dealing with—just on a much larger scale.
Constrained vs Unconstrained Demand in Different Industries
The idea isn’t limited to factories.
Manufacturing
The main constraints may be machinery, labor, materials, and production capacity.
Retail
Inventory availability, replenishment, distribution, and store capacity can affect what customers are able to purchase.
Logistics
Vehicle capacity, drivers, warehouse space, transportation lanes, and equipment availability can limit fulfillment.
Hospitality
A hotel may have more potential customer demand than the number of rooms it can sell on a particular night.
Airlines
Available seats and booking controls can limit how much observed demand turns into actual bookings.
The terminology and calculations can vary by industry and planning system, but the underlying issue is similar: observed transactions don’t always show the full demand that existed.
Common Misunderstandings
“Unconstrained demand means unlimited demand.”
No.
It doesn’t mean customers will buy an unlimited amount.
It means the demand estimate isn’t reduced simply because the business currently has a supply limitation.
“Constrained demand is always bad.”
No.
A constrained plan is necessary when the business needs to create a realistic operational plan.
The problem is not using constraints. The problem is allowing those constraints to completely hide the underlying demand opportunity.
“Sales always equal demand.”
Not necessarily.
Sales can be lower than demand when products are unavailable, orders are rejected, capacity is insufficient, or customers face other restrictions.
“The unconstrained forecast should be sent directly to production.”
Not necessarily.
The unconstrained view helps establish what the market may require. Supply planning then determines what can actually be supported and what actions are needed to close the gap.
Frequently Asked Questions
What is the simplest difference between constrained and unconstrained demand?
Unconstrained demand is what customers are expected to want without supply limitations. Constrained demand reflects what can realistically be fulfilled after those limitations are considered.
Which is better for demand forecasting?
An unconstrained demand view is generally preferable as the starting point for forecasting because it prevents current supply limitations from automatically becoming the forecast. Constraints can then be considered during supply planning and S&OP.
Can constrained demand be lower than unconstrained demand?
Yes. That’s one of the main reasons for having the two views.
If customers want 10,000 units but the business can support only 7,000, the supply constraint creates a 3,000-unit gap.
Why is constrained demand sometimes based on historical sales?
Because historical sales are often readily available. The problem is that historical sales may have been affected by stockouts or other restrictions, so they shouldn’t automatically be treated as a perfect measure of underlying demand.
What is demand unconstraining?
Demand unconstraining is the process of estimating demand that was hidden or reduced by supply limitations, such as stockouts, capacity restrictions, or booking limits.
How does this relate to S&OP?
S&OP brings demand and supply together. The unconstrained view helps establish what the business expects customers to want, while the constrained view helps determine what the supply chain can realistically support. The difference between the two becomes an important management discussion.
Is constrained demand the same as constrained supply?
Not exactly.
Constrained supply refers to what the supply network can provide under its limitations.
Constrained demand can refer to the demand plan after those supply limitations have been considered.
The terminology can differ between planning systems, so businesses should always check how their specific system defines each measure. SAP planning discussions, for example, distinguish a constrained supply plan from a subsequently adjusted constrained demand plan.
Final Takeaway
The easiest way to remember the difference is to ask two questions.
Unconstrained demand:
“If we had enough supply, how much would customers want?”
Constrained demand:
“Given what we currently have, how much can we realistically support?”
Neither question replaces the other.
If you look only at unconstrained demand, your plan may ignore operational reality. If you look only at constrained demand, you may mistake a supply problem for weak demand.
The real value comes from seeing both.
When the two numbers are compared, the gap between them becomes useful information. It can tell you where inventory is too low, where capacity is holding back growth, where suppliers need attention, and where the business may have an opportunity worth investing in.
That’s why, in good demand planning, the goal isn’t simply to choose constrained or unconstrained demand.
It’s to understand both—and know why they are different.
