When to reorder Amazon inventory based on velocity and lead time.
Inputs
1.0=normal, 2.0=Q4 peak
Restock urgency
Days of cover—
Order by
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Stockout date (no order)
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Recommended order qty
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About this calculator
Amazon inventory management is unforgiving. Run out of stock and Amazon\'s algorithm punishes you for weeks afterward — your BSR drops, organic ranking craters, and buy box wins decline. The cost of a single 5-day stockout often exceeds the cost of carrying excess inventory for months.
This calculator does the math: current stock ÷ daily sales = days of cover. If days of cover < (lead time + safety stock), you should be ordering now. The calculation accounts for seasonal multipliers — Q4 peak periods need 2× the normal cover because demand spikes faster than reorders can ship.
The reorder quantity recommendation aims for ~90 days post-arrival cover (lead-time + safety + reasonable forward stock). For seasonal categories, multiply by the seasonal factor. Conservative operators add another 20% buffer; lean operators run tighter and accept more frequent reorder cycles.
Pair with the Amazon FBA Fees calculator (per-unit cost economics) and the Reorder Point calculator (general inventory math). For Q4 readiness, also use the BFCM Planner to project peak-season demand spikes against current FBA stock.
Frequently asked questions
How often does Amazon penalize stockouts?
Heavily. Stockouts kill BSR (Best Seller Rank), tank organic ranking, and lose your buy box. Recovery takes 4-8 weeks of full stock + ad spend to rebuild ranking. Single 5-day stockouts can cost 30-50% of monthly revenue beyond the stockout window itself.
What's a safe Amazon inventory cover?
45-60 days normally. 90+ days going into Q4 (BFCM stockouts are catastrophic). Below 30 days you risk algorithm penalties and tighter restock limits from Amazon. The Amazon "IPI" (Inventory Performance Index) score also factors here — running too lean dings IPI.
How does Amazon's restock limit work?
Amazon caps how much inventory you can ship into FBA based on sell-through rate and IPI score. New sellers and slow-moving products face tighter limits. Plan accordingly — you can't always ship the volume you'd want when you want.
Should I use FBA or FBM?
FBA for 80%+ of products that benefit from Prime badge and buy-box advantages. FBM (you ship) for oversized items where FBA fees are punitive, slow-moving SKUs (storage fees crush economics), or out-of-FBA periods during restock issues.
What about long-term storage fees?
Amazon charges aging fees for inventory sitting 365+ days, plus monthly storage rate increases for slow movers. Avoid by keeping turnover above 4× annually. Slow movers should be either liquidated, removed and sent to a 3PL, or pulled to FBM to avoid fee compounding.