Safety Stock Calculator
Enter your demand and lead-time data to calculate the safety stock quantity you need to prevent stockouts at your desired service level.
Use the Safety Stock Calculator
Inventory Inputs
80%
85%
90%
95%
97.5%
99%
Fill in the inputs and click Calculate to see your safety stock.
Safety Stock
—
units
Reorder Point
—
units
Avg Lead Demand
—
units
Formula Breakdown
Safety Stock by Service Level
| Service Level | Z-Score | Safety Stock | Reorder Point |
|---|
Summary
Safety stock is the extra inventory kept on hand to guard against demand spikes and supply delays. This calculator uses the standard statistical formula — Z × √(Lead Time) × Demand Std Dev — plus an extended version that also accounts for lead-time variability. Enter your inputs, pick a service level, and get your safety stock quantity and reorder point in seconds.
How it works
- Enter the average daily (or weekly) demand for the product.
- Enter the standard deviation of demand over the same time unit.
- Enter the average supplier lead time in the same time unit.
- Optionally enter the standard deviation of lead time for a more accurate result.
- Choose a service level (fill rate) — higher service levels require more safety stock.
- The calculator outputs safety stock quantity and the reorder point.
Use cases
- Prevent stockouts during peak seasons without over-ordering.
- Set reorder points that account for supplier variability.
- Compare safety stock requirements across different service levels.
- Justify buffer inventory to finance teams with a statistical basis.
- Reduce carrying costs by right-sizing safety stock instead of guessing.
- Plan inventory for new products based on forecast uncertainty.
Frequently Asked Questions
Last updated: 2026-06-11 · Reviewed by Nham Vu