Safety Stock Calculator
Estimate safety stock from a service-level z value, daily demand variability and a fixed lead time.
How to use this calculator
- Supply a service-level z value, daily demand standard deviation and lead-time duration.
- Check the labels and units before using a result outside this page.
- Change one input at a time if you want to compare scenarios.
Formula and method
Safety stock = z × standard deviation of daily demand × √(lead-time days)
- Safety stock = z × standard deviation of daily demand × √(lead-time days)
- The model assumes a fixed lead time and a suitable demand distribution; use a different model when demand or lead time varies materially.
Worked examples
Worked example
z = 1.65, daily-demand standard deviation 4, lead time 9 days.
Safety stock ≈ 1.65 × 4 × 3 = 19.8, rounded up to 20 units.
Safety stock ≈ 1.65 × 4 × 3 = 19.8, rounded up to 20 units.
Understanding the result
Estimate safety stock from a service-level z value, daily demand variability and a fixed lead time.
The model assumes a fixed lead time and a suitable demand distribution; use a different model when demand or lead time varies materially.
Important notes
The model assumes a fixed lead time and a suitable demand distribution; use a different model when demand or lead time varies materially.
Displayed outputs are rounded for readability; preserve full precision when continuing a calculation.
Frequently asked questions
What does this safety stock calculator show?
Estimate safety stock from a service-level z value, daily demand variability and a fixed lead time.
Which inputs should I check first?
Supply a service-level z value, daily demand standard deviation and lead-time duration.
Can the result be used as a final professional specification?
The model assumes a fixed lead time and a suitable demand distribution; use a different model when demand or lead time varies materially.
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.