If you're a wholesaler, importer, or distributor, stockouts on your best-selling items are the fastest way to lose customers. Your A-SKUs—the 20% of products that drive 80% of revenue—can't be out of stock. Ever.
Yet stockouts happen constantly in operations that rely on gut feel, spreadsheet reviews, or manual reorder triggers. By the time someone notices the shelf is empty, you've already lost sales and maybe lost the customer to a competitor.
This guide shows how to use your WMS to set intelligent reorder points, calculate safety stock, and automate alerts—so you never run out of what matters most.
Understanding A/B/C Classification
Before setting reorder points, you need to know which SKUs matter most:
A-SKUs (Top 20% by revenue/velocity)
- Represent ~80% of your sales volume or revenue
- Stock-sensitive: a stockout immediately impacts revenue
- Deserve the tightest reorder controls
B-SKUs (Next 30%)
- Represent ~15% of sales
- Important but less critical than A-items
- Moderate safety stock appropriate
C-SKUs (Bottom 50%)
- Represent ~5% of sales
- Long tail items, slow movers
- Minimal safety stock, accept some stockout risk
Your WMS should automatically classify SKUs based on sales velocity or revenue. Reclassify quarterly—a seasonal product might be an A-item in Q4 and a C-item in Q2.
Calculating Reorder Points
A reorder point (ROP) is the inventory level that triggers a replenishment order. The formula:
ROP = (Average Daily Demand × Lead Time) + Safety Stock
Example for SKU "Widget-A":
- Average daily demand: 50 units
- Lead time from supplier: 14 days
- Safety stock: 200 units (we'll calculate this below)
ROP = (50 × 14) + 200 = 900 units
When inventory drops to 900 units, trigger a purchase order.
Key considerations:
- Use actual demand data, not forecasts alone
- Account for demand variability (more variable = higher safety stock)
- Update lead times based on recent supplier performance, not contracts
- Review ROPs quarterly or when demand patterns shift
Calculating Safety Stock
Safety stock is your buffer against uncertainty—demand spikes, supplier delays, or receiving errors. The basic formula:
Safety Stock = Z × σ × √Lead Time
Where:
- Z = service level factor (1.65 for 95%, 2.33 for 99%)
- σ = standard deviation of daily demand
- Lead Time = in days
For A-SKUs, target 98-99% service level (Z = 2.05-2.33) You can't afford stockouts on these items.
For B-SKUs, target 95% service level (Z = 1.65) Acceptable to occasionally run short.
For C-SKUs, target 90% service level (Z = 1.28) Low-volume items don't justify high safety stock costs.
Example:
- Daily demand std dev: 15 units
- Lead time: 14 days
- Service level: 98% (Z = 2.05)
Safety Stock = 2.05 × 15 × √14 = 115 units
Round up to 120 for practical purposes.
Example Workflow: Automated Replenishment
Here's how a WMS handles replenishment for a wholesale distributor:
Monday 8:00 AM – Inventory check
- Widget-A: 950 units on hand, ROP = 900 ✓ (above threshold)
- Widget-B: 280 units on hand, ROP = 300 ⚠️ (below threshold)
- Gadget-C: 45 units on hand, ROP = 100 ⚠️ (below threshold)
Monday 8:15 AM – Alert triggered
- 2 SKUs below reorder point
- Suggested PO quantities based on economic order quantity
Monday 9:00 AM – PO created
- Widget-B: Order 500 units (EOQ), lead time 7 days
- Gadget-C: Order 200 units (EOQ), lead time 10 days
Monday 2:00 PM – Expected receipt logged
- Widget-B: ETA next Monday
- Gadget-C: ETA week after
Friday – Demand spike
- System shows: 180 current + 500 on order = 680 units expected
- At current velocity, safe until PO arrives Monday
Following Monday – Receipt
- 500 units received → inventory now 620 units
- Status: above ROP, no action needed
No stockout occurred because the system triggered the order at the right time.
Setting Up Replenishment in Your WMS
Effective automated replenishment requires:
Item-level parameters
- Reorder point (calculated or manually set)
- Safety stock level
- Economic order quantity (EOQ) or min/max order quantities
- Primary supplier and lead time
- ABC classification
Supplier master data
- Lead times per supplier (not just averages—track actual performance)
- Minimum order quantities
- Order multiples (e.g., must order in cases of 12)
Alert configuration
- Below ROP alerts → Purchasing team
- Critical stockout risk (below safety stock) → Urgent/escalation
- Lead time exceeded alerts → Supplier management
Demand history System needs 6-12 months of sales data to calculate averages and variability accurately.
WarePulse lets you set all these parameters at the item level, run nightly replenishment checks, and generate suggested purchase orders automatically.
Min/Max vs. Reorder Point Systems
Some operations prefer min/max inventory systems:
Min/Max approach:
- Minimum = Reorder point
- Maximum = Target inventory level after replenishment
- Order quantity = Max - Current inventory
Pros:
- Simpler to understand and maintain
- Good for stable demand items
Cons:
- Doesn't optimize order quantities
- Can result in frequent small orders or infrequent large orders
ROP + EOQ approach:
- ROP triggers the order
- EOQ determines how much to order (balances ordering cost vs. holding cost)
Pros:
- Optimizes total inventory cost
- Better for high-volume items
Cons:
- Requires more data and calculation
- EOQ assumes stable demand
Recommendation for wholesalers: Use min/max for C-SKUs (simple, low stakes) and ROP + EOQ for A/B-SKUs (worth the optimization).
Common Replenishment Mistakes
Avoid these pitfalls:
1. Using stale lead times Supplier contracts say 7 days; reality is 12 days. Use actual receipt data to update lead times.
2. Ignoring demand variability Averages lie. A SKU with 100 units/day average but 50-150 range needs more safety stock than one with 95-105 range.
3. Setting and forgetting Review A-SKU parameters monthly, all SKUs quarterly. Demand shifts, suppliers change, seasonality matters.
4. Not accounting for on-order inventory Your reorder check should consider: On-hand + On-order - Allocated = Available for ROP comparison.
5. Ordering too late If your ROP is 900 and you check weekly, you might not catch when inventory drops to 850 until it's at 600. Check daily or use real-time alerts.
Take Control of Your Inventory
Stockouts on A-SKUs are preventable. With the right WMS configuration:
- Classify SKUs by velocity and revenue impact
- Set reorder points based on actual demand and lead times
- Calculate safety stock appropriate to service level targets
- Automate alerts so you never miss a reorder trigger
WarePulse gives wholesalers and distributors the tools to manage replenishment proactively. Real-time inventory visibility, automated reorder alerts, and suggested PO quantities mean you spend less time fighting fires and more time growing your business.
Ready to stop the stockouts? Explore WarePulse for distribution or check out our cycle counting guide to ensure your inventory data is accurate enough to trust.