Stock and manufacturing glossary
Safety stock
Safety stock is the extra quantity of an item you keep to cover demand that is higher than expected or deliveries that arrive late. It is the buffer that prevents a stock-out while you wait for your next order, at the cost of money tied up in stock.
Why it matters to your business
Sales and deliveries never run exactly to plan. A customer places a large order, or a vendor’s truck is held up for three days. Safety stock is what lets you keep selling through those surprises. The skill is keeping enough to protect sales on the items that matter, without locking your working capital in a warehouse full of buffers.
How it works
A pharmacy distributor sells an average of 20 boxes a day of a common medicine, but up to 30 on busy days. The vendor usually delivers in 7 days, but has taken up to 10.
Safety stock = (30 × 10) − (20 × 7) = 300 − 140 = 160 boxes.
At a cost of ₹250 a box, that buffer ties up ₹40,000. The reorder point becomes 20 × 7 + 160 = 300 boxes. For a medicine that customers expect to find every time, that is a fair price for reliability. For a slow item that sells twice a month, a buffer this size would be wasted money.
With expiry dates involved, sell the oldest batches first so the buffer keeps turning over rather than expiring on the shelf.
Common mistakes
- The same buffer for every item. Keep safety stock where a stock-out loses a customer, and little or none for slow or easily substituted items.
- Never revising it. As sales grow or vendors become more reliable, the right buffer changes. Review it at least before each season.
- Treating it as spare stock. If the buffer is regularly used up, your reorder point or lead time assumption is wrong, not the buffer.
- Forgetting expiry. Buffers of short-life goods need rotating, or they turn into write-offs.
Questions about Safety stock
What is the difference between safety stock and the reorder point?
Safety stock is the buffer itself. The reorder point is the level at which you order, which is the stock you expect to sell during the lead time plus the safety stock.
How do I calculate safety stock?
A simple method is (maximum daily sales × maximum lead time) minus (average daily sales × average lead time). Larger businesses use statistical methods based on how much sales and lead times vary.
How much safety stock should I keep for seasonal items?
Base it on sales during the season, not the yearly average, and raise it before the season starts. Reduce it again as the season ends, so you are not left with the extra.
Does safety stock cost money?
Yes. It ties up cash, uses warehouse space and can expire or go out of fashion. Keep it for items where a stock-out is costly, not for everything.
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