Inventory calculator
Safety Stock Calculator
Estimate how much extra stock covers a busy spell or a late delivery, using a simple maximum-versus-average method. Your entered values stay out of analytics.
Formula and assumptions
Safety stock = maximum daily usage × maximum lead time − average daily usage × average lead time. A negative result is shown as zero.
- This is the simple max-versus-average method for small businesses. It is not a statistical service-level model.
- Maximum figures are the worst case you want to cover, such as your busiest day and your slowest supplier.
- Use one unit throughout.
- Shown to 2 decimal places. A negative result is shown as 0.
Formula version 1.0, last reviewed 1 October 2026.
Frequently asked questions
What should I use as the maximum?
Your busiest realistic day and your slowest realistic delivery, not a once-in-a-decade extreme. Look at your last few months of records.
Is this a statistical service-level calculation?
No. It is a simple method suited to small businesses. A statistical method needs demand history and a target service level.
What happens if I swap maximum and average by mistake?
The calculator warns you when a maximum is below its average, and shows zero rather than a negative buffer.