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Estimate average transit inventory from demand and transit time, then calculate an actual cutoff balance from shipment and receipt rows. Work through units, operational value, reconciliation checks, and the separate question of accounting ownership.
The in transit inventory formula for an estimated average is demand per day × average transit days. Actual units at a reporting cutoff require shipment and receipt records: dispatched units less received units, with documented losses or other resolutions handled separately. Neither calculation determines which company should recognize the goods in its accounts.
Estimated average transit units = Daily flow rate × Average transit days
Actual open transit units = Dispatched units − Matched received units − Documented resolved units
Operational transit value = Sum of open units × Applicable unit cost for each line
The first formula answers a planning question: how many units would normally sit between dispatch and receipt? For a stable lane where shipments replenish demand, demand per day can be a practical proxy for the daily flow rate. If shipments and demand are diverging, use the relevant actual flow rate or describe the demand-based figure as a planning estimate.
The relationship follows Little's Law: average units in a system equal the arrival rate multiplied by average time in that system. John Little's original paper also emphasizes consistent definitions of the system, arrivals, and time spent. For this article, the boundary is physical dispatch through receipt, rather than purchase order placement through delivery.
The second formula answers a cutoff question. Which dispatched units remain unreceived now? An average estimate cannot identify those shipments. Keep the estimate and actual balance in separate columns rather than forcing them to match.
Use a shipment-line export and a receipt-line export covering the same cutoff. Keep the shipment ID, shipment line, purchase order reference, SKU, origin, destination, base unit, dispatch timestamp, dispatched quantity, and expected receipt date. Receipts need the matching shipment line, receipt timestamp, and received quantity.
If one shipment has several receipts, total those receipts before comparing them with the dispatch line. Otherwise, joining the files can repeat the dispatched quantity for every receipt and inflate the apparent stock in transit.
For the planning estimate, bring daily demand or flow history and completed transit durations for the same SKU and lane. Define whether days are calendar or business days. Use that definition in both inputs. The transit reliability worked example covers shipment timing comparisons without turning a timing result into an inventory ownership rule.
A US distributor reviews two filter SKUs. It assumes stable daily replenishment equal to demand, uses calendar days, and values the example at constant unit acquisition cost. All figures below are operational estimates.
| SKU and lane | Demand, units/day | Average transit, days | Estimated units | Unit cost (USD) | Estimated value (USD) |
|---|---|---|---|---|---|
| F-20 to Chicago | 80 | 6 | 480 | 18 | 8,640 |
| G-10 to Denver | 40 | 5 | 200 | 30 | 6,000 |
| Total | 680 | 14,640 |
F-20 is 80 × 6 = 480 units, valued at 480 × 18 = $8,640. G-10 is 40 × 5 = 200 units, valued at 200 × 30 = $6,000. The total is 480 + 200 = 680 units and $8,640 + $6,000 = $14,640. Units are exact in this illustration; no rounding is required.
To test a faster F-20 lane, change only transit time from six calendar days to four. The estimate becomes 80 × 4 = 320 units, or 320 × 18 = $5,760. That is 160 fewer average units and $2,880 less operational value in transit under the stated assumptions. It is not a forecast of an immediate cash receipt.
At September 30, 2026, the distributor's dispatch and receipt files contain these shipment lines. Receipts shown are cumulative matched receipts through the cutoff. There are no documented loss resolutions in this example.
| Shipment | SKU and destination | Dispatched units | Received units | Open transit units | Unit cost (USD) | Open value (USD) |
|---|---|---|---|---|---|---|
| S-101 | F-20, Chicago | 600 | 200 | 400 | 18 | 7,200 |
| S-102 | F-20, Chicago | 900 | 900 | 0 | 18 | 0 |
| S-103 | G-10, Denver | 240 | 0 | 240 | 30 | 7,200 |
| Total | 1,740 | 1,100 | 640 | 14,400 |
The quantity proof is 1,740 dispatched = 1,100 received + 640 still open. Line S-101 remains open for 600 − 200 = 400 units; receiving part of it does not close the remainder. S-102 contributes zero. S-103 contributes 240 units. Value is 400 × 18 + 0 × 18 + 240 × 30 = $14,400.
If dispatched units are in C2 and matched receipts in D2, the remaining quantity is =C2-D2 before any documented resolutions. Investigate a negative result rather than hiding it with a zero floor: it could reveal duplicate receipts, a wrong shipment match, or a missing dispatch correction.
| SKU | Estimated average units | Actual open units | Actual minus estimate |
|---|---|---|---|
| F-20 | 480 | 400 | -80 |
| G-10 | 200 | 240 | 40 |
| Total | 680 | 640 | -40 |
Actual operational value is $14,400 against the estimated $14,640, a difference of -$240. F-20 accounts for -$1,440, while G-10 accounts for +$1,200. The comparison directs investigation; a single cutoff can differ from a long-run average because shipments arrive in batches.
Tie the 1,100 received units to receiving records, then to the receipt movements in the site's inventory on hand calculation. Those units cannot remain in the physical transit bucket after receipt. Keep this check separate from inventory safety stock, which addresses uncertainty rather than the ordinary time goods spend moving.
For US tax inventory, IRS Publication 538 says purchased merchandise is included when title has passed, even if it is still in transit, and excludes future deliveries where title has not passed. That is a tax rule, not a blanket conclusion about financial statement recognition from a dispatch flag.
Give the controller the contract references and shipment evidence needed to assess the company's accounting treatment. The $14,400 example is a quantity-times-cost operational value, not an automatically approved carrying amount. Days inventory outstanding should use the appropriate accounting inventory balance rather than an unreviewed logistics total.
Bring your dispatch lines, matched receipts, demand history, transit durations, and unit costs to Covirage. Covirage maps the columns; its tools compute and check the supplied figures, and the external AI model explains the comparisons with every figure traced to its rows. Create a free Covirage account, set up your business, and bring a sample of your own export; creating the account takes about a minute.
See Covirage for supply chain teams for the wider business context.
No. An open purchase order can include goods that have not been dispatched. A physical transit report starts with a defined dispatch event and ends with receipt or documented resolution. Broader procurement pipeline measures may include supplier processing time, so label their boundaries explicitly.
That depends on the applicable accounting policy and the facts of the transaction, including contract terms and evidence of ownership or control. A shipped or unreceived status is insufficient by itself. Finance should review the operational shipment report separately before determining accounting treatment.
Match each receipt to its shipment and line, then subtract only the quantity received by the cutoff. The remaining quantity stays open until it arrives or has a documented resolution. Do not close the entire shipment because its first carton was received.
With the same steady flow rate and scope, fewer transit days imply fewer average units between dispatch and receipt. That is a planning relationship. Actual balances can still rise temporarily because of batching, delayed receipts, seasonal demand, or changes in the quantities shipped.