Reorder Level Calculator
At what level should you place an order? It finds the critical level from daily sales and lead time.
Equivalent to how many days of sales
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Safety Stock Calculator
Safety stock is the reserve quantity you hold on top of your normal needs so you don’t run out when sales move faster than expected or a supplier is late. This tool subtracts the average case from the worst case (highest daily sales × longest lead time) to calculate how large the buffer should be; it also separates how much of the buffer comes from sales fluctuation and how much from supplier delays — so you can see which problem to solve to reduce your tied-up cash.
Safety Stock Calculator
Safety stock
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hold on top of normal needs
From sales fluctuation
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how far off the forecast is
From supplier delays
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how late the supplier is
Reorder point
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including safety stock
The real problem
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For the highest sales and the longest lead time, don’t use a single extreme day; take the few worst cases from the last three months. A one-off unusual day leads you to hold a larger buffer than you need.
Calculation formula
Emniyet stoğu = (En yüksek günlük satış × En uzun tedarik süresi) − (Ortalama günlük satış × Ortalama tedarik süresi) Satış dalgalanmasından gelen pay = (En yüksek satış − Ortalama satış) × Ortalama tedarik süresi Tedarik gecikmesinden gelen pay = (En uzun süre − Ortalama süre) × En yüksek günlük satış Sipariş noktası = (Ortalama satış × Ortalama tedarik süresi) + Emniyet stoğu
Example: a shop that sells 12 units a day and gets stock in 7 days
You sell an average of 12 units a day, rising to 20 on busy days. The supplier normally delivers in 7 days; on the worst occasion it took 12.
Worst case: 20 × 12 = 240 units. Normal case: 12 × 7 = 84 units. Safety stock: 240 − 84 = 156 units — about 13 days of your sales.
Of these 156 units, 56 come from sales fluctuation ((20 − 12) × 7) and 100 from supplier delays ((12 − 7) × 20). So the real problem is your supplier’s lateness: if you could bring the longest delivery time down from 12 days to 9, your buffer would drop from 156 to 96 units — 60 units less cash tied up. Talking to the supplier rather than fixing your forecast frees up more money here.
Measure the two numbers, don’t guess them
This calculation rests on two real measurements, and both can be collected in a few weeks.
Highest daily sales: total the movement records in the inventory tracking template by day and look at the busiest days of the last 90 days.
Longest lead time: record the date you place an order and the date the goods enter the warehouse in the order tracking template. What counts is the time you measured, not the time the supplier quotes.
If your stock sits in a separate warehouse rather than on the shop shelf, these two numbers come out right only if receipts and issues are recorded per warehouse: if goods arriving at the warehouse and goods sold aren’t recorded on the same day, “highest daily sales” looks lower than it really is and your buffer is calculated smaller than needed. How to keep receipt, issue and stocktake records in a warehouse is explained step by step in the guide how to track warehouse stock.
The difference between safety stock and the reorder point
They are not the same thing, and mixing them up leads you to order either too early or too late.
Safety stock is the untouched buffer — under normal conditions you never use it. The reorder point is the level at which you say “order now”, and it includes the safety stock: the quantity you will sell during the lead time + safety stock.
In the example above, safety stock is 156 and the reorder point is 84 + 156 = 240 units. You place an order when stock falls to 240; if everything goes well, you still have 156 units on hand when the goods arrive. To calculate the reorder point and the suggested order quantity directly, use the reorder level calculator.
What does it cost if the buffer is large?
Safety stock isn’t free: every unit sitting on the shelf is tied-up cash. To measure how much stock you carry, see the inventory turnover calculator — it is the first metric to drop when you raise safety stock.
For products with an expiry date, enlarging the buffer also increases the risk of spoilage. For such products, ordering more often (buying less, more frequently) is usually cheaper than enlarging the safety stock.
Frequently asked questions
What is safety stock?
Safety stock is the reserve quantity held on top of normal needs so you don’t run out when sales move faster than expected or a supplier is late. It isn’t used under normal conditions; it only comes into play when things go badly.
How is safety stock calculated?
The most common method that a small business can apply is this: (Highest daily sales × Longest lead time) − (Average daily sales × Average lead time). You measure both extreme values from your own records; no statistics knowledge is needed.
Is safety stock the same as buffer stock?
Yes, they are two names for the same concept (in Turkish, “emniyet stoğu” and “güvenlik stoğu”); in English it is “safety stock”. “Emniyet stoğu” is the term used more often in logistics.
Is safety stock different from the critical stock level?
Yes. Safety stock is the buffer itself; the critical stock level (reorder point) is the total level at which you need to order, including that buffer. Reorder point = quantity sold during the lead time + safety stock.
Don’t I need to use the standard deviation formula?
The formula Z × standard deviation × √lead time gives a more precise result for businesses that keep daily sales data regularly and whose fluctuation is close to a normal distribution. Most small businesses don’t have this data; the highest–average method solves the same problem with two measurable numbers and a similar result.
Should I calculate it separately for each product?
Ideally yes, because sales speed and lead time vary by product. In practice, calculating it for the 20–30 products that generate most of your revenue is enough; holding a buffer on slow-moving products is often a loss.
What does it mean if the result is zero or negative?
If the highest sales you entered equals the average sales and the longest lead time equals the average lead time, there is no fluctuation; that product needs no safety stock. In practice, this can be a sign that no measurement was made — take the extreme values from real records.
Related calculators
Inventory Turnover
How many times a year does your stock turn over, in how many days does it sell out, and how much cash is tied up in the warehouse?
To keep this calculation in Excel
Inventory Tracking Excel
Automatically calculates remaining stock from incoming and outgoing movements, the low-stock alert, and total stock value.
Order Tracking Excel
Tracks orders by channel, status, amount and shipping tracking number; calculates delivery time in days.
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Last updated: September 18, 2026