What is a reorder point?
The reorder point (ROP) is the on-hand inventory level that should trigger your next replenishment — a purchase order or a production run. Set it correctly and the stock left when you reorder is just enough to carry you through the lead time, plus a buffer for the things that don't go to plan.
The reorder point formula
ROP = d × L + safety stock
d = average daily demand · L = lead time (days) · safety stock = buffer for demand & lead-time variability
A reorder point without safety stock (just d × L) breaks even with demand — you'd stock out half the time. The safety stock term is what holds your service level. This calculator carries that buffer in directly from the Z-score safety stock step, so the two numbers always agree.
Days of cover — a quick sanity check
Dividing the reorder point by daily demand gives the days of cover. If your lead time is 7 days and your days of cover is around 10, the extra ~3 days is your safety buffer expressed in time. It's a fast way to gut-check whether the trigger level looks reasonable on the shop floor.
Frequently asked questions
What is a reorder point?
The inventory level at which you place a new order or start a production run. When stock drops to the ROP, what's left should just cover demand until replenishment arrives.
What is the reorder point formula?
ROP = (d × L) + safety stock, where d is average daily demand and L is lead time in days. Without safety stock it's simply d × L.
How is the reorder point related to safety stock?
Safety stock is one of the two parts of the ROP. d × L covers expected demand during lead time; safety stock covers the variability on top of that.
What is days of cover?
The reorder point divided by average daily demand — how many days of demand the trigger level represents. A quick check against your lead time.