Risk Pooling Safety Stock Centralization Calculator
Holding safety stock at each warehouse duplicates protection that one central pool could provide. This calculator quantifies the saving from pooling, based on how many sites you have and how correlated their demand is.
Your numbers
0 means independent, 1 means sites move together.
Your results
Pooling saves stock but adds transport time and cost to customers. Compare the saving with the service and freight impact before consolidating.
Safety stock vs number of locations pooled
Sweeps Number of locations from 1 to 20, holding your other inputs fixed.
Network inventory review
Optional: we can analyse multi-site stock and demand correlation from your ERP data.
Optional. The tool and every export work without this. No spam.
How to use it
Enter the number of sites, the daily demand standard deviation at a typical site, the correlation between sites, lead time, service level, unit cost and carrying rate. The tool compares the sum of site-level safety stocks with the safety stock of one pooled location and values the difference.
- Estimate correlation from weekly demand across sites
- Use the same service level in both cases
- Run it per item family, not once for the whole range
The method
Separate sites need n times z times sigma times the square root of lead time. Pooled demand has a standard deviation of sigma times the square root of (n + n(n - 1) times rho). With rho at zero this is the classic square root law: safety stock falls to about one over the square root of n of the separate total. At rho of one, pooling saves nothing.
Reading the result
The chart shows separate safety stock growing linearly with the number of sites, while pooled safety stock grows slowly. Gains are largest for many sites with uncorrelated demand and expensive items. Move the correlation slider to see how regional demand patterns erode the benefit.
Common mistakes
Ignoring the downside is the big one: central stock means longer delivery to customers and higher freight. Another error is assuming zero correlation when sites serve the same customers. Consider keeping a small forward stock for fast movers and pooling slow movers, which is a common hybrid in ERP distribution setups.
Frequently Asked Questions
What is risk pooling?
Combining demand from several locations into one stock lowers relative variability, because high demand at one site tends to offset low demand at another. That lets you hold less safety stock for the same service level.
Why does correlation matter?
If sites move together, their highs and lows coincide and cancel less. Positive correlation reduces pooling benefit, and perfect correlation eliminates it. Independent or negatively correlated demand pools best.
What is the square root law?
With independent, identical sites, pooled safety stock is the separate total divided by the square root of the number of sites. Four sites merged into one cut safety stock by about half.
What should I weigh against the saving?
Delivery time to customers, outbound freight, emergency transfer costs, customs for cross-border pooling and contractual service commitments. A saving in stock can be erased by higher freight on every order.
If you want to test consolidation scenarios against real site-level demand in your ERP, Netray can build that model with you.
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