A reorder point (ROP) is the threshold that prompts a replenishment decision. For a basic continuous-review policy:
Reorder point = expected demand during lead time + safety stock
Retail buyers use it to decide when to review another supplier order. It does not tell you the order quantity or guarantee that stock will last until delivery.
How to calculate a reorder point
With average daily demand d and lead time L in days, expected lead-time demand is d × L. Use matching units: bottles per day multiplied by days gives bottles, not cases.
Under fixed lead time and independent daily demand with constant variance, a normal-approximation buffer is z × σd × √L. Here σd is daily-demand standard deviation and z corresponds to the chosen cycle service target. Variable lead times, correlated demand and sparse sales require different treatment. See safety stock for the assumptions.
Cycle service level measures the probability of avoiding a stockout during a replenishment cycle; it is not the percentage of units fulfilled. MIT's inventory lecture distinguishes these service measures and inventory policies.
Worked retail example
This fictional example assumes:
| Input | Value |
|---|---|
| Average daily demand | 12 bottles |
| Fixed lead time to usable stock | 4 days |
| Daily-demand standard deviation | 3 bottles |
| Cycle service target | Approximately 95%, using z = 1.65 |
- Expected lead-time demand:
12 × 4 = 48 bottles. - Safety stock:
1.65 × 3 × √4 = 9.9 bottles. - Reorder point:
48 + 9.9 = 57.9, rounded up to 58 bottles.
The threshold is not a request to order 58 bottles. Choose the new quantity using a separate order policy, then check supplier pack sizes, minimums, storage and cash constraints. Try the reorder point calculator to inspect the arithmetic.
Compare the threshold with inventory position
Inventory position includes on-hand and on-order stock, less backorders and commitments. Define those demand deductions without counting the same obligation twice. On-hand stock alone can give a different signal.
Continue the fictional example:
| Record | Bottles |
|---|---|
| Usable on hand | 40 |
| Outstanding supplier order | 24 |
| Unfilled commitments, not already deducted | 10 |
| Inventory position | 54 |
40 + 24 − 10 = 54, below the 58-bottle trigger. If the existing supplier order were 48 bottles instead, inventory position would be 78. That changes the new-order decision even though the shelf count is still 40.
Timing still matters. An order arriving after the expected shortage cannot prevent that shortage. Inspect the outstanding quantity, confirmation and expected receipt date. A canceled order, unusable delivery or unreliable ETA needs an exception decision; an aggregate inventory-position number does not resolve it.
The incoming-stock review workflow focuses on this check before another order is placed.
Reorder point versus PAR and order quantity
A reorder point is a trigger. An order-up-to target, often called a PAR level, defines a desired position. Continuous-review policies can order a fixed quantity when the trigger is reached or order up to a target. Periodic policies review on a schedule; their coverage must consider the interval until the next review as well as lead time.
For the fictional 54-bottle inventory position, a separately chosen target of 120 would leave a 66-bottle gap. If a supplier sells only 12-bottle cases, six cases supply 72 bottles, bringing the position to 126. Review the six-bottle excess against available space and expected use. This example illustrates pack rounding; it does not establish that 120 is the right target.
EOQ is another way to examine order quantity under its own cost and demand assumptions. Setting safety stock to zero does not by itself implement a just-in-time operating system.
Is days of cover the same signal?
Only when the stock basis matches and the average demand rate is positive. Dividing the 58-bottle threshold by 12 bottles per day gives about 4.83 days. Dividing inventory position by the same demand rate preserves that comparison; dividing only on-hand stock does not when incoming orders or commitments differ.
On-hand coverage is still useful for inspecting when the shelf may empty. Keep that question separate from whether another order would duplicate stock already purchased. If demand is zero, highly intermittent or distorted by stockouts, a simple coverage ratio may be uninformative.
What to review before placing the order
| Check | Buyer question |
|---|---|
| Demand basis | Do these sales represent demand, or was the item unavailable for part of the period? |
| Lead time | Does the assumption include the time until goods are usable, including receiving? |
| Incoming orders | Is the outstanding quantity still confirmed, at the right location and in the right units? |
| Commitments | Have reservations and backorders been deducted exactly once? |
| Supplier constraints | Can the supplier deliver the proposed packs by the required date? |
| Physical stock | Do counts, damage and expiry make the recorded quantity misleading? |
Review inputs when supplier performance, the assortment, promotions or observed demand changes. Choose a routine cadence that fits the item and buying schedule, then check results. Recalculating daily cannot predict an unseen demand spike or make a late delivery arrive sooner.
Evaluating the workflow in LineNow
LineNow connects replenishment review with purchase orders, supplier changes and receiving. Its configured replenishment rules include stock thresholds, days of stock and lead-time coverage. The rule named “reorder point” uses order-frequency coverage and a configured buffer; it should not be assumed to reproduce the statistical lead-time formula above. Confirm the selected rule and its inputs during setup.
Bring one SKU, one outstanding order and one partial receipt to a demonstration. Ask the team to show:
- Which stock and demand records feed the recommendation.
- Which trigger and quantity policy apply to this item.
- How outstanding quantities and case-to-unit mappings affect the result.
- Where the buyer reviews and sends the purchase order.
- How a supplier change and receipt remain attached to the living purchase order.
If calculation is the only task, start with the free calculator. If the challenge is moving from a recommendation to a reviewed supplier order, explore inventory replenishment software for retailers. For a sent order whose date or quantity has changed, use PO status tracking.