Planning calculator
Safety Stock Calculator
Set a practical inventory buffer using demand variability over replenishment lead time.
What this calculator does
- Estimate buffer stock from demand variation, lead time, and a service factor.
- Use when setting inventory buffers for purchased or manufactured parts with variable demand.
- Estimate buffer stock from demand variation, lead time, and a service factor.
Formula used
- Safety stock = service factor × demand standard deviation × √lead time
- Lead-time demand = average daily demand × lead time
- Protected quantity = lead-time demand + safety stock
Inputs explained
- Average daily demand: undefined
- Daily demand standard deviation: undefined
- Lead time: undefined
- Service factor: undefined
How to use the result
- Use when setting inventory buffers for purchased or manufactured parts with variable demand.
- This is a planning calculator. Validate assumptions against your process data before using the result as a final quote, schedule, or engineering decision.
Common questions
- Which inputs usually drive the safety stock result? average daily demand, daily demand standard deviation, lead time, and service factor usually have the biggest effect. When one of those assumptions changes, rerun the calculator and compare the new units result before updating the plan.
- What does the safety stock calculator do? Estimate buffer stock from demand variation, lead time, and a service factor.
- What inputs do I need for the safety stock calculator? You need average daily demand, daily demand standard deviation, lead time, and service factor. Use measured values from your line, quote package, supplier data, or current production plan whenever possible.
- How should I interpret the safety stock result? Treat the units output as a planning estimate for planning work. Compare it against process history, quoted assumptions, and operating limits before making final decisions.
Last reviewed 2026-05-12.