Safety Stock Calculator
Buffer stock and reorder point.
Enter your values
Enter the average daily demand you are working with.
Enter the demand std deviation you are working with.
Enter the lead time in days.
Choose one of: 90%, 95%, 99%.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Safety stock
- 139
- Reorder point
- 1,219
- Lead time demand
- 1,080
- Days of cover
- 1.2
Quick answer
Safety stock buffers demand and lead-time variability to hit your target service level.
Safety stock = Z × SD × √lead time
At a glance
| What it does | Buffer stock and reorder point. |
|---|---|
| Category | Business |
| Inputs needed | Average daily demand, Demand std deviation, Lead time, Service level |
| Main output | Safety stock |
| Formula | Safety stock = Z × SD × √lead time |
| Cost | Free — no sign-up, no download |
How to use the Safety Stock Calculator
- 1Enter average daily demand and its standard deviation.
- 2Enter supplier lead time.
- 3Choose the service level you need.
Inputs explained
- Average daily demand
- Enter the average daily demand you are working with.
- Demand std deviation
- Enter the demand std deviation you are working with.
- Lead time(days)
- Enter the lead time in days.
- Service level
- Choose one of: 90%, 95%, 99%.
Worked example
Using the values the calculator loads with:
Inputs
- Average daily demand120
- Demand std deviation28
- Lead time9 days
- Service level95%
Results
- Safety stock139
- Reorder point1,219
- Lead time demand1,080
- Days of cover1.2
Frequently asked questions
Why not just hold more stock?
Every extra unit ties up cash and risks obsolescence.
What service level should I use?
95% for most items, 99% for critical lines.
What do I need to enter into the Safety Stock Calculator?
Just 4 values: average daily demand, demand std deviation, lead time, service level. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Safety Stock Calculator work out the answer?
Safety stock buffers demand and lead-time variability to hit your target service level. It applies the formula Safety stock = Z × SD × √lead time and shows the working so you can check each step by hand.
Is the Safety Stock Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.