In-Transit Pipeline Inventory and Safety Stock Cost Calculator
Long lanes tie up money in two ways: goods on the water that you own but cannot use, and extra stock held to cover late arrivals. This calculator puts a yearly price on both.
Your numbers
From historical ship and receipt dates. 20 to 30 percent of the mean is common for ocean lanes.
Your results
Safety stock here covers transit variability only, with demand treated as steady. Add demand variability and supplier delay for a full safety stock figure.
Annual lead time cost vs transit variability
Sweeps Std deviation of transit time from 0 to 20, holding your other inputs fixed.
Lane lead time analysis from ERP history
Optional: discuss measuring real transit time and variability by supplier and lane from your ERP receipts.
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How to use the pipeline inventory calculator
Enter annual volume on the lane, the landed cost per unit and the average door-to-door transit time. Add the standard deviation of transit time, which you can calculate from past ship and receipt dates in your ERP, the service level you want and your annual carrying rate. The result shows pipeline units and value, the yearly cost of carrying them, the extra safety stock due to transit variability and the combined yearly cost of the lead time.
The formulas
Pipeline inventory equals average daily demand times transit days, which is Little's law applied to the lane. Its value is that quantity times landed cost. Safety stock for transit variability equals the service factor Z times daily demand times the standard deviation of transit days. Annual carrying cost for each is value times the carrying rate. The total is the sum. Z comes from the normal distribution, for example 1.64 at 95 percent and 2.33 at 99 percent.
- Halving transit time halves pipeline inventory.
- Halving variability halves safety stock.
- Raising service level from 95 to 99 percent adds about 42 percent more safety stock.
Using the result in sourcing decisions
Compare this cost with the unit price advantage of the far source. If an offshore supplier saves 1.50 per unit on 120,000 units, that is 180,000 a year; if the lead time cost here is 70,000, the saving is real but smaller than the quote suggests. The chart shows how much variability costs: reducing transit variability through better carrier selection, fewer transshipments or consolidated schedules can be worth as much as shortening the average time.
Common mistakes
Use door-to-door time, including supplier handover, export clearance, port dwell and inland delivery, not just the sailing time. Do not use ship dates from the supplier's schedule; use actual receipt dates from your goods receipt records. Pipeline inventory is often owned by you from the Incoterm transfer point, so check whether you pay for it from FOB or only from delivery. Also note that this tool assumes steady demand; seasonal products need a separate peak estimate.
Frequently Asked Questions
What is pipeline inventory?
It is the stock you own that is in transit between the supplier and your site. It is calculated as average daily demand multiplied by the average transit time, and it counts as working capital even though you cannot use it.
How do I find the standard deviation of transit time?
Export purchase order ship dates and goods receipt dates for the lane, calculate the difference in days for each shipment, and take the standard deviation of those values. Twelve months of history is a good starting point.
Does ownership transfer matter?
Yes. Under FOB or FCA you take ownership at origin, so the pipeline value is on your balance sheet. Under DAP or DDP the supplier owns it in transit, and you may pay for that in the price instead.
Is this the full safety stock?
No, it covers only the part caused by transit variability. A complete figure also includes demand variability and supplier production variability, combined as the square root of the sum of squares.
Netray can calculate actual transit time variability by lane directly from purchase order and goods receipt history in your ERP.
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