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Safety Stock Calculator

Estimate buffer inventory for independent daily demand variation and a fixed replenishment lead time.

Use a consistent reporting periodCheck the calculation below
Business dashboard
Business dashboard

Use figures from the same reporting period.

See the method

Enter your business figures

Runs on your device

Your key metric

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter standard deviation of daily demand, fixed lead time, cycle service level, mean daily demand.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

Safety stock = z × daily-demand standard deviation × sqrt(lead-time days). Reorder point = mean daily demand × lead time + safety stock.

A WORKED EXAMPLE

Using standard deviation of daily demand = 12 units/day, fixed lead time = 9 days, cycle service level = 1.644853627, mean daily demand = 80 units/day, the result is 60 units. Change these example inputs to match your task; use the method above to check each step.

Understanding your result

No. This model holds lead time fixed. Supplier variability, correlated demand, trends and intermittent sales require a different inventory model.

What to keep in mind

Assumes independent daily demand, fixed lead time and a normal lead-time demand approximation. Service level means probability of no stockout per cycle, not fill rate. Use consistent currencies, reporting periods and accounting definitions. This arithmetic estimate excludes items not entered in the form.

Common questions

Does this cover unpredictable supplier delays?

No. This model holds lead time fixed. Supplier variability, correlated demand, trends and intermittent sales require a different inventory model.

Are business inputs stored?

This tool calculates locally in your browser. It does not upload your figures or connect to your business accounts.

Methodology maintained by ClarityKit. How these tools are built and checked.