About the Safety Stock Calculator
Safety stock using the max-usage method or a service-level (z-score) formula with demand variability.
Also known as: buffer stock, safety stock formula, service level stock.
How to use this calculator
- Enter method, average daily usage, average lead time (days) and the other fields.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
Max method: (max usage × max lead) − (avg usage × avg lead) · Statistical: z × σ × √lead time
Worked example
Using the values pre-filled in the calculator above:
- Method: Max usage − average usage
- Maximum daily usage = 70
- Maximum lead time (days) = 10
- Average daily usage = 45
- Average lead time (days) = 7
the calculator returns:
- Safety stock: 385 units
- Reorder point: 700