Work out spare parts stock level instantly with clear inputs, formula shown and shareable results.
The reorder point is expected demand during the supplier lead time plus safety stock sized from the variability of that demand and the service level required. For spares the service level should reflect the cost of a stockout, which for a critical machine part is the whole downtime cost.
Reorder point
ROP = daily usage x lead time + z x standard deviation of lead-time demand
Service factors
z = 1.282 for 90%, 1.645 for 95%, 2.326 for 99%
No. Criticality analysis should split spares into insurance items held regardless of usage, routine consumables managed by reorder point, and items best sourced on demand.
Normal-distribution safety stock breaks down for intermittent demand. Use a Poisson or Croston-based model, or set stock from the consequence of a stockout rather than a service level.