Ecommerce & Shopify · 100% free

Reorder Point Calculator

When to reorder a SKU, accounting for lead time, sales velocity and a safety-stock buffer.

Shopify WooCommerce Cin7 Inventory Planner
Reorder when stock drops to
954 units
Lead-time demand 875 + safety stock 79
Lead-time demand
875
Avg daily sales × lead time
Safety stock
79
~3 extra days of demand cover
Inventory cost at ROP
$13,343
Working capital locked at trigger
How safety stock is calculated: z-score × demand standard deviation × √(lead time). The z-score scales with service level — 1.65 covers 95% of lead-time demand variability. If your demand swings wildly (seasonal, viral, COVID-like), raise std deviation; if lead times are unreliable, raise lead time average rather than std deviation.

About this tool

Reorder Point (ROP) = (daily sales × lead time days) + safety stock. Get this number wrong on a hero SKU and you stock out for weeks, killing PMax / Meta CBO momentum that takes months to rebuild. Compute ROP, safety stock from demand variability, and total inventory required.

Service level translates to stockout risk

  • • 90% — stockout ~10% of cycles. Use for low-margin / commoditised SKUs only.
  • • 95% — stockout ~5%. Industry default for ecommerce.
  • • 97% — stockout ~3%. For important SKUs with strong ad spend.
  • • 99% — stockout ~1%. Hero SKUs that anchor your paid campaigns.

Lead time honesty

The number one cause of stockouts isn't bad math — it's overly optimistic lead times. Use the 90th-percentile lead time you've historically experienced (not the supplier's promise), and add a conservative buffer if you're shipping from overseas.

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