How the Safety Stock Calculator works
Safety stock absorbs the difference between what you expect and what happens. The statistical method sizes it from how variable your daily sales are and how long the lead time is.
Formula
- Simple: Daily sales × Safety days
- Statistical: z × σ(daily sales) × √Lead time
- Max demand: Max daily × Max lead − Avg daily × Avg lead
Example
Statistical buffer of about 25 units at 95% service.
Average daily sales: 10Safety days (simple method): 14Lead time (days): 25Daily sales std dev (statistical): 3Service level z: 1.65
Frequently asked questions
How do I get the standard deviation?
Export 60–90 days of unit sales and use STDEV in a spreadsheet.