Reorder Point Calculator

The reorder point (ROP) is the stock level that triggers your next purchase order. Set it right and the new shipment arrives just as you're about to run out; set it wrong and you either stock out (costing sales) or carry excess inventory (costing cash).

Two formulas, one shape

Basic and advanced modes share the lead-time stock term; they differ only in how safety stock is computed:

Basic: ROP = D̄ × L + D̄ × S_days | Advanced: ROP = D̄ × L + Z × σ × √L

Worked example

Average demand 20 units/day, lead time 7 days, safety buffer 5 days:

1. Lead-time stock = 20 × 7 = 140 units
2. Safety stock = 20 × 5 = 100 units
3. Reorder point = 140 + 100 = 240 units
4. Place the next PO when inventory falls to 240
5. Advanced (σ=5, 95% service): safety = 1.65 × 5 × √7 ≈ 22 → ROP 162

Practical tips

• Use the last 3 months of sales for average daily demand — older data drifts.
• Lead time is door-to-door, including customs clearance for imported goods.
• Service level 95% is the conventional B2C target; 99% for medical / pharma / critical SKUs.
• If demand is highly seasonal, recompute ROP each quarter — a single annual figure under-buffers peaks.
• Pair ROP with Economic Order Quantity (EOQ) — ROP tells you when, EOQ tells you how much.