How Much Safety Stock Should a Small Business Keep?
By Ty Fisher, founder of Fisher Software
Safety stock is the extra inventory you keep because real life is less predictable than a spreadsheet. Sales spike, suppliers run late, shipments arrive short, and a product that looked safe on Monday can be gone by Friday. The goal is not to keep a huge cushion on every SKU. It is to keep enough extra stock on the items where running out would hurt, while avoiding shelves full of cash that is not moving.
Start with the reason you need a buffer
Safety stock should protect against a specific kind of uncertainty. For one product, the problem may be unpredictable demand. For another, it may be a supplier that sometimes delivers three days late. If both demand and lead time are stable, a large buffer may not be necessary.
Use a simple starting calculation
Safety stock ≈ average daily sales × extra days of protection
If an item sells about four units a day and you want three extra days of protection, a starting buffer is 12 units. This is not a perfect forecasting model, but it gives a small business a useful baseline that can be adjusted with experience.
Give more protection to the products that matter most
- Fast sellers that generate regular revenue.
- Products customers expect you to have immediately.
- Items with long or inconsistent supplier lead times.
- Products that are difficult to substitute when unavailable.
- Seasonal items where a missed selling window cannot be recovered later.
Do not use the same safety stock for every SKU
A blanket rule such as “keep two weeks of everything” is easy to manage but expensive. Slow-moving products can sit for months while fast sellers still run out. Group products by sales pace, margin, supplier reliability, and stockout risk, then set different buffers for each group.
Separate safety stock from your reorder point
Safety stock is the reserve. The reorder point is the inventory level that tells you it is time to place another order. A practical reorder point combines expected demand during supplier lead time with the safety stock you want to keep in reserve.
Recheck the number when conditions change
- A supplier begins taking longer to deliver.
- Sales speed up or slow down.
- A new location starts drawing from the same inventory.
- Seasonality changes demand.
- Storage space or cash becomes tighter.
- Repeated stockouts show that the current buffer is too small.
Watch for the opposite problem: too much protection
Excess safety stock has a cost too. Cash is tied up, storage fills, older products can become obsolete, and slow-moving items hide purchasing mistakes. If a product repeatedly ends the month with far more stock than needed, lower the buffer or order smaller quantities more often.
Make safety stock part of a regular purchasing review
Do not set the number once and forget it. Review important items on a schedule and compare actual sales, supplier delivery time, stockouts, and leftover inventory. The best safety-stock level is the smallest buffer that reliably protects the business from the uncertainty that actually occurs.