Reorder Point Calculator
Compute the reorder point with the standard formula ROP = (D × LT) + Safety Stock. Find the stock level at which to trigger the next PO. Updates live as you type.
Inputs
Mean units sold or consumed per day for this SKU. Weekly demand ÷ 7 if you only have weekly.
Average days from PO placed to stock-in-warehouse, including freight and customs.
Don't know your safety stock? Use our safety stock calculator first, then bring the number back here.
Result
How to use the calculator
Three inputs, one trigger. The maths is easy — the hard part is sourcing reliable daily demand and an honest supplier lead time.
- 1
Enter average daily demand
Units sold or consumed of this SKU on an average day. Use a recent window — 8 to 13 weeks of sales data — to capture the current trend without being thrown by stale or seasonal extremes.
- 2
Enter supplier lead time in days
Average time from PO placed to stock-in-warehouse, including freight and customs. If your lead time varies a lot week to week, that variability belongs in safety stock, not here.
- 3
Enter safety stock in units
The buffer you hold to protect against demand or supply variance. If you don't know it yet, run the safety stock calculator first — set this to zero and the result becomes a plain lead-time demand figure.
- 4
Read the reorder point
When stock-on-hand drops to this number of units, place the next PO. The maths assumes you'll receive the new stock right as you run out of the cycle stock, with the safety stock untouched.
- 5
Use days of cover as a sanity check
Days of cover at the reorder point is how many days of stock you'll be holding when the trigger fires. If it's lower than your supplier's actual lead-time variability, your safety stock is too thin.
The reorder point formula, briefly
The formula is:
Two halves. D × LT is lead-time demand — the units you expect to sell during the wait for the next PO to land. Safety Stock is the buffer that protects against demand or supply running hotter than expected.
The point of holding the buffer separately is that you can dip into it without placing an emergency order — that's what it's for. The reorder point is the trigger that fires before the buffer is exposed.
For the deeper explanation, read the reorder point glossary entry. Connected concepts: safety stock, lead time, and lead-time variability.
What actually changes the answer
Average daily demand (D)
Linear scaling. Double daily demand and the reorder point doubles (assuming safety stock is recomputed against the new variance). The risk: stale D figures during demand ramps cause stockouts because the trigger is set too low for the current run rate.
Lead time (LT)
Linear scaling on the lead-time-demand half — every extra day of lead time adds one more day's worth of demand to the trigger. Long offshore lead times push reorder points up sharply.
Safety stock
Direct addition. Larger buffer = higher trigger. Driven mostly by demand and lead-time variability and the target service level — see the safety stock calculator for sizing.
Demand or lead-time drift
A reorder point set six months ago is rarely the right trigger today. Demand drifts with seasonality and channel mix; lead times drift with supplier capacity. Refresh per SKU at least quarterly.
Common reorder point mistakes
- →Conflating reorder point with safety stock. The reorder point is the trigger; safety stock is the buffer. Treating them as the same number means either ordering too early (high working capital) or too late (stockouts).
- →Using nominal lead time instead of average actual. The supplier's quoted lead time and your actual delivered lead time differ for most brands by 10–30%. Use the actual.
- →Ignoring lead-time variability. A 21-day average lead time with ±5 days variance needs more buffer than 21-day average with ±1 day variance. Push that variability into safety stock with the full formula in the safety stock calculator.
- →Setting one ROP and never updating it. Demand and lead time drift continuously. A reorder point isn't a one-shot calculation — it's a quarterly review.
Frequently asked questions
What is the reorder point formula?+
Reorder Point = (Average daily demand × Lead time in days) + Safety stock. The first half is the lead-time demand — the units you expect to sell while waiting for the next PO to land. The second half is the buffer that protects against the lead-time demand running hot or the supplier running late.
How is reorder point different from safety stock?+
Safety stock is the buffer. Reorder point is the trigger. Safety stock answers 'how much should I hold in case things go wrong'. Reorder point answers 'at what stock level should I place the next order'. ROP is always larger than safety stock because it also has to cover normal demand during the lead time.
What if I don't have a safety stock number yet?+
Two options. Set safety stock to zero and the calculator returns lead-time demand only — the bare-minimum trigger that assumes no variance at all. Or run the safety stock calculator first to compute a buffer from your demand variability, lead-time variability, and target service level, then bring the number back here. The second is what most growing brands need.
Should I use daily or weekly demand?+
Use daily for fast-movers (50+ units a day) where daily variance is meaningful. Use a daily-equivalent (weekly demand ÷ 7) for slower SKUs where daily numbers are too noisy. The formula's only requirement is that demand and lead time are in the same time unit — if both are weekly, the result is still right.
What if my lead time is variable?+
Lead-time variability belongs in the safety stock figure, not the reorder point itself. Use the average lead time here, then compute safety stock with both demand variability and lead-time variability — the safety stock calculator switches to the full formula when you enter lead-time σ. The reorder point will widen accordingly.
Does the reorder point need to be recomputed often?+
Yes. Demand drifts with seasonality and channel mix. Lead times drift with supplier capacity and freight conditions. Refresh per SKU at least quarterly, and on any major supplier change. A reorder point computed in Q4 of last year is rarely the right trigger this quarter.
Why is my reorder point sometimes higher than my max stock cap?+
Three usual causes. (1) The SKU is fast-moving with long offshore lead times — physical reality, not a maths error. (2) Demand has grown materially since the last cap was set. (3) Safety stock is sized for a service level that doesn't match the SKU's commercial value — drop service level a tier for tail SKUs to compress the buffer.
How does reorder point fit with EOQ?+
ROP answers 'when to order'. EOQ answers 'how much to order'. Together they form the classic continuous-review policy — every time stock-on-hand hits the reorder point, you place an order of EOQ size. Safety stock cushions the gap if demand or lead time runs hot. None of the three works well in isolation.