What it means
A backorder sits between two outcomes. In a full stockout the sale is simply lost, while in a backorder the customer stays but the order becomes more expensive to serve, so the cost is not the whole sale but the erosion around it.
The tangible components are easy to list: air freight or express courier charges to catch up, split shipments that double the delivery cost, extra picking and packing runs, and staff time spent on status calls and chase emails. The intangible components matter more over time, since a customer who waits twice usually shops around the third time.
Measuring backorder cost matters because it is one side of a trade-off. Holding more safety stock raises carrying costs, so a business only knows how much buffer inventory is worth having once it can put a figure on what running short actually costs.
Most companies estimate the cost per backordered unit rather than trying to capture it perfectly. They add up expediting spend, allocate a share of customer service payroll, and apply an observed cancellation rate to the lost contribution margin, which is enough precision to drive an inventory policy.
Inventory models treat the assumption explicitly. A full backorder model assumes every unstocked demand waits, a lost sale model assumes none do, and real businesses sit somewhere in between, so the partial backorder assumption usually produces the most sensible safety stock recommendation.
In practice
Real-world examples.
Example
An online furniture retailer backorders 900 sofas after a container delay. It ships 300 of them by expedited road freight at an extra $95 each and offers a $50 credit to the rest, so the incident costs $28,500 in freight and $30,000 in credits.
Example
A hospital supplies distributor runs short of surgical gloves and splits deliveries across two shipments for 400 accounts. The additional picking, packing and carrier charges add $18 per account, an unplanned $7,200 for the month.
Example
A consumer electronics brand takes pre-orders and backorders a popular headphone model for seven weeks. Cancellation data shows 18% of those orders drop out, and the finance team uses that rate to justify a larger safety stock ahead of the next product cycle.
Formula
Calculation
Total backorder cost = expediting cost + additional handling cost + (units cancelled x contribution margin per unit)
Cost per backordered unit = total backorder cost / units backordered
A distributor of industrial fasteners backorders 5,000 units in a quarter. Expedited inbound freight to fill those orders costs $4.00 per unit, or $4.00 x 5,000 = $20,000, and additional customer service and split-shipment handling runs at $2.50 per unit, or $2.50 x 5,000 = $12,500.
Historically 12% of backordered units are cancelled before delivery, which is 5,000 x 12% = 600 units. At a contribution margin of $22 per unit, the lost margin is 600 x $22 = $13,200.
Total backorder cost for the quarter is $20,000 + $12,500 + $13,200 = $45,700, which works out at $45,700 / 5,000 = $9.14 per backordered unit. Since the annual cost of holding one extra unit of safety stock is about $6.00, the numbers argue for a larger buffer on this product line.Case study
Seen in the real world.
Brightpath Supply Co is a fictional distributor invented to illustrate how backorder costs are measured. Its management had always treated backorders as a service annoyance rather than a financial item, and the operations report simply showed a monthly backorder percentage with no dollar figure attached.
A new finance analyst pulled three quarters of data and priced the problem: $9.14 per backordered unit once expediting, handling and cancellation losses were counted, against a safety stock carrying cost of about $6.00 per unit per year. Across roughly 20,000 backordered units a year, the cost was around $183,000.
Brightpath raised safety stock on its forty highest-volume lines, adding about $75,000 of carrying cost while removing an estimated $130,000 of backorder cost. Just as importantly, the backorder percentage became a line in the monthly management pack with a dollar value beside it. The illustrative point is that an operational metric only changes behaviour once someone attaches money to it.
Watch out
Common mistakes.
- Counting only the freight. Expediting is usually the smallest part, and the cancellation losses plus staff handling time often add up to more than the shipping premium.
- Treating every backorder as a retained sale. A meaningful share of waiting customers cancel or buy elsewhere, so applying an observed cancellation rate is essential to getting the figure right.
- Comparing backorder cost to the product price rather than to inventory carrying cost. The decision is a trade-off against holding stock, so contribution margin and carrying cost are the relevant comparators.
Questions
People also ask.
How is a backorder different from a stockout?
A stockout is the condition of having no stock, while a backorder is what happens when a customer places an order anyway and waits for fulfilment.
Should backorder costs appear in the financial statements?
They are already scattered across freight, payroll and lost revenue rather than shown as one line, which is exactly why a separate management estimate is useful.
What is a reasonable target backorder rate?
It depends on the industry, but many distributors aim for the low single digits as a percentage of order lines, balanced against what the extra safety stock costs.
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