Safety stock is the cushion that keeps a bad week from becoming a stockout. The reorder point is the on-hand level that tells you to buy. Together they decide whether you ever run dry.
Safety stock and reorder point are the two numbers that govern when and how much to reorder so you neither stock out nor drown in inventory. They are different quantities that work together. Safety stock is a buffer you hold. Reorder point is a trigger level you watch. Confusing them is the most common reason a reorder system fails.
Safety stock is the extra inventory you hold beyond expected demand to protect against two kinds of surprise: demand running hotter than your average, and a reorder arriving later than planned. It is insurance against variability. If your sales and your lead times were perfectly steady, you would need none. They never are, so you hold a cushion.
The right amount scales with two things: how volatile demand is, and how unreliable your lead time is. A SKU that sells a steady 20 units a day with a supplier who always delivers on time needs a thin buffer. A SKU whose sales spike unpredictably, supplied by a vendor whose lead time swings from 30 to 50 days, needs a much fatter one.
A simple, defensible method expresses safety stock as a number of days of average demand:
Safety stock = Average daily demand x Buffer days.
If you sell 20 units a day and you want a 7-day cushion, safety stock is 140 units. The buffer-days choice encodes your risk tolerance. More volatile SKU or flakier supplier, more buffer days. The trade-off is real: more safety stock means fewer stockouts but more cash tied up in inventory, which drags your inventory turnover (/glossary/inventory-turnover-ratio).
The reorder point is the on-hand quantity at which you place a new order. It is set so that the reorder arrives just as you would otherwise start eating into your safety stock. The formula:
Reorder point = (Average daily demand x Lead time in days) + Safety stock.
The first term covers demand during the lead-time window, the units you will sell while you wait for the order. The second term is the safety stock you want untouched when the order lands. Add them and you get the level that, when hit, means "order now."
| INPUT | VALUE |
| Average daily demand | 20 units |
| Lead time | 30 days |
| Buffer days for safety stock | 7 days |
| Safety stock (20 x 7) | 140 units |
| Demand during lead time (20 x 30) | 600 units |
| Reorder point (600 + 140) | 740 units |
When on-hand stock across all locations falls to 740, you place the order. Over the next 30 days you sell about 600 units, drawing down toward your 140-unit buffer, and the reorder arrives to refill before the buffer is breached. That is the system working.
Think of it as a staircase. Safety stock is the floor you never want to fall through. The reorder point sits above it by exactly one lead time's worth of demand, so hitting the trigger and waiting out the lead time lands you back near the floor, not below it. Set the reorder point too low and you breach safety stock and risk a stockout. Set it too high and you reorder early, carry excess, and trap cash.
This is the engine behind reorder forecasting, walked through step by step in forecasting inventory reorders (/blog-posts/forecast-inventory-reorders). The glossary defines the parts; the how-to runs the loop.
Both formulas depend on three inputs being accurate: daily demand, lead time, and on-hand stock. For a multi-channel seller, each is easy to get wrong.
ConnectBooks supplies the demand and on-hand sides. It tracks sales velocity across channels from settlement data, and ConnectStock, its multi-location inventory feature, keeps a live on-hand count across FBA, 3PL, home warehouse, and in transit. With complete, current inputs, your safety stock and reorder point are accurate rather than stale. ConnectStock is bundled with Platinum and available as an add-on on Gold and Diamond.
Safety stock is the buffer inventory you hold to absorb demand spikes and lead-time delays. Reorder point is the on-hand level that triggers a new order. Safety stock is a quantity you keep; reorder point is a threshold you watch. The reorder point includes safety stock plus expected demand during the lead time.
Multiply average daily demand by lead time in days, then add safety stock. At 20 units a day, a 30-day lead time, and 140 units of safety stock, the reorder point is (20 x 30) + 140 = 740 units. When on-hand stock hits that level, you order.
Enough to cover demand and lead-time variability, sized to the SKU. A common method is average daily demand times a chosen number of buffer days. More volatile demand or less reliable suppliers call for more buffer days; the cost is more cash tied up in inventory.
Yes. Base daily demand on total sales of the SKU across every channel. Using one channel's demand understates the true rate, pushes the reorder point too low, and causes stockouts.
Almost always because an input is stale or incomplete: demand from one channel only, an optimistic lead time, or an on-hand count that misses 3PL or in-transit stock. Live, complete inputs, like the all-location count ConnectStock maintains, fix the misfires.
Keep safety stock and reorder points accurate with a live, all-channel count. See ConnectStock at /pricing.
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