Reorder Point and Safety Stock: Two Lines, Two Jobs in EDGEBIC

In EDGEBIC by User Solutions a reorder point and safety stock are two separate levels with two different jobs: the reorder point is the timing trigger that fires a replenishment when the projected balance falls to it, and safety stock is the buffer that flags a bucket when the balance drops below it, so the reorder point sits above safety stock and the gap between them is the room a replenishment needs to arrive. Keeping the two straight is what makes the difference between reordering in time and reordering too late.

This post explains each level's job, why the reorder point belongs above safety stock, and how to size the gap between them. For the buffer's role in absorbing variability, see how safety stock absorbs demand variability, and for the wider loop start from the EDGEBIC planning guide.

Two Levels, Tracked Separately

EDGEBIC carries a reorder point and a safety stock as distinct settings on a product, and it treats them as distinct signals. That separation is deliberate, because they answer different questions.

The reorder point answers when to start restocking. When the projected balance falls to the reorder point in a bucket, a replenishment suggestion fires. It is a timing trigger.

Safety stock answers how much cushion to hold. It is the buffer you keep against demand variability, and when the balance drops below it, the bucket is flagged. It is a level to defend.

Because they are separate, a product can have a reorder point of 80 that starts the restock and a safety stock of 20 that marks the cushion. Two numbers, two roles.

Why the Reorder Point Sits Above Safety

The whole arrangement works only if the reorder point is higher than safety stock. Here is why.

As demand pulls the balance down bucket by bucket, it reaches the reorder point first, because that level is higher. At that moment the suggestion fires, while the buffer below is still whole and untouched. You have started the restock with the full cushion still intact. If the replenishment arrives before the balance falls further, you never touch safety stock at all.

Now imagine the reorder point set below safety stock. The balance would cross the buffer first, eroding it, and only then hit the reorder point and fire a suggestion. You would begin restocking after the buffer was already spent, which defeats the purpose of holding one. The buffer exists to be a last line, not the trigger.

So the ordering is not a preference. It is what makes the buffer a buffer.

The Gap Is Lead-Time Demand

The distance between the reorder point and safety stock is not arbitrary. It should equal the demand you consume during the replenishment lead time.

The logic is straightforward. When the suggestion fires at the reorder point, the replenishment does not arrive instantly; it takes a lead time. During that lead time, demand keeps drawing stock down. If the gap between the reorder point and safety stock covers exactly that lead-time demand, then when the order lands, the balance has fallen from the reorder point to right about safety stock, and the incoming supply refills it without the buffer being breached.

So the formula for the reorder point is:

reorder point = safety stock + (demand rate x lead time)

If you use 20 a week, hold a safety stock of 40, and it takes three weeks to replenish, lead-time demand is about 60, and the reorder point should be about 100. The suggestion fires 60 units above the buffer, giving the replenishment exactly the room it needs.

A Worked Example: Sizing Both Levels

Take a part with weekly demand of 45 and a replenishment lead time of two weeks. You decide, from your tolerance for variability, that you want a safety cushion of 50 units.

Lead-time demand is 45 times 2, which is 90. So the reorder point should be safety stock plus lead-time demand: 50 plus 90, which is 140.

Now the plan behaves well. The balance falls to 140, the suggestion fires, and over the next two weeks demand pulls it down by about 90 to roughly 50. The replenishment lands right as the balance nears the buffer, refills it, and the cushion was never spent. Set the reorder point at 50 instead, equal to the buffer, and you would fire the order only at the buffer and dip below it every cycle.

Both, Not Either

The common temptation is to use one level and skip the other. Neither alone works. With only a reorder point, you have a trigger but no defined cushion to protect, so variability has nothing to absorb it. With only safety stock, you have a cushion but no early signal, so you reorder only when you hit it and arrive late.

Together they cover both concerns. Safety stock is the size of the cushion, set from how much variability you need to absorb. The reorder point is the timing, set from safety stock plus lead-time demand, so the order fires early enough to arrive before the cushion is touched. Set them as a pair and the plan reorders in time, every cycle.

Keeping the Two Lines Right

Read the reorder point as when and safety stock as how much. Keep the reorder point above the buffer by your lead-time demand, and revisit both when your usage rate or supplier lead time changes, since the gap is only correct as long as those inputs hold. Get them right and a replenishment suggestion fires with the full cushion intact, every time.

For how the reorder trigger method compares with a min-max target, read min-max vs reorder-point replenishment, and for when safety stock becomes a strict floor, read when safety stock becomes a hard floor. For the trigger concept in general terms, see the reorder point glossary.