Amazon Inventory Replenishment Guide: Never Run Out of Stock Again
Running out of stock on Amazon is one of the most damaging events for your seller account. Stockouts cause your Best Seller Rank (BSR) to drop, your keyword rankings to fall, and your advertising costs to spike when you relaunch.
This guide teaches you a proven inventory replenishment system that keeps your Amazon FBA stocked — without over-ordering.
Why Inventory Replenishment Matters
The Cost of Stockouts
| Impact | Description |
| Lost sales | Every day out of stock = lost revenue (avg. $5 , –$2 , , /day per ASIN) |
| BSR drop | Best Sellers Rank drops quickly when inventory runs out, making recovery harder |
| Keyword ranking loss | Ranking can fall 5 , %+ within 3–5 days of stockout |
| PPC cost increase | Click-through rate drops on out-of-stock listings; ACOS rises |
| Buy Box loss | Competitors can take the Buy Box during stockouts |
| IPI score impact | Stockouts negatively affect your Inventory Performance Index |
The Cost of Overstocking
| Impact | Description |
| Long-term storage fees | $ , . , 5–$6.9 , per cubic foot per month ( , 8 , + days) |
| Capital tied up | Cash locked in inventory that isn’t selling |
| Aged inventory surcharge | Additional 5%– , , % fee on inventory 27 , + days old |
| Storage limits | Amazon may reduce your storage allowance |
The goal: Order the right quantity at the right time — not too much, not too little.
Understanding Amazon’s Inventory Metrics
Key Metrics to Track
| Metric | What It Means | Target |
| Days of Supply | How many days your current inventory will last | 3 , –45 days |
| Sell-Through Rate | Units sold ÷ units in stock (over 3 , days) | > , , % |
| Excess Inventory | Units with 9 , + days of supply | < , , % of inventory |
| Stranded Inventory | Units at FBA but not listed for sale | , |
| IPI Score | Amazon’s overall inventory health score | >5 , , (ideally >7 , , ) |
| Replenishment Rate | How quickly you restock after selling | Within lead time |
Amazon Inventory Performance Index (IPI)
Your IPI score determines your storage limits:
| IPI Score | Storage Limit Impact |
, –399 | Restricted storage; potential quarter-over-quarter limits |
| 4 , , –499 | Standard storage limits |
| 5 , , –699 | Good standing: flexible limits |
| 7 , , + | Excellent: maximum flexibility |
How to Calculate Your Reorder Point
Your Reorder Point (ROP) is the inventory level at which you should place a new order with your supplier.
Formula
,
>
Definitions
- Average Daily Sales: Total units sold in last 3
,
days ÷ 3
,
- Lead Time: Total days from placing order to FBA receiving (production + shipping + receiving)
- Safety Stock: Buffer inventory to handle unexpected demand spikes or shipping delays
Example Calculation
Let’s say you sell a kitchen gadget:
| Variable | Value |
| Monthly sales (3 , days) | 6 , , units |
| Average daily sales | 6 , , ÷ 3 , = 2 , units/day |
| Production time | , , days |
| Sea freight time (LCL) | 3 , days |
| FBA receiving time | 5 days |
| Total lead time | 45 days |
| Safety stock (7 days) | 7 × 2 , = , 4 , units |
Reorder Point = (2
,
× 45) +
,
4
,
= 9
,
,
+
,
4
,
=
,
,
,
4
,
units
→ When your FBA inventory drops to
,
,
,
4
,
units, place a new order immediately.
How to Calculate Reorder Quantity
Your Reorder Quantity (ROQ) is how many units to order each time.
Formula
,
>
Example Calculation
| Variable | Value |
| Monthly sales (3 , days) | 6 , , units |
| Average daily sales | 6 , , ÷ 3 , = 2 , units/day |
| Production time | , , days |
| Sea freight time (LCL) | 3 , days |
| FBA receiving time | 5 days |
| Total lead time | 45 days |
| Safety stock (7 days) | 7 × 2 , = , 4 , units |
Reorder Quantity = (2
,
× 6
,
) +
,
4
,
–
,
,
,
4
,
=
,
,2
,
,
+
,
4
,
–
,
,
,
4
,
= 3
,
,
units
Wait — that doesn’t seem right. Let’s recalculate:
Actually, reorder quantity should cover the next reorder cycle:
Reorder Quantity = Average Daily Sales × Reorder Cycle = 2
,
× 6
,
=
,
,2
,
,
units
The safety stock is already built into your reorder point. So you order enough to last until the next reorder.
Choosing Your Reorder Cycle
Lead Time Management
| 3 , days | Low capital tied up; fresh inventory | Frequent ordering; higher per-unit shipping cost | New products, low-volume sellers |
| 6 , days | Balanced; moderate shipping costs | Moderate capital commitment | Established products |
| 9 , days | Lowest per-unit cost; FCL possible | High capital; risk of excess inventory | High-volume, stable sellers |
Typical Lead Time Breakdown
| Stage | Sea Freight (LCL) | Air Freight |
| Order placement to production start | , –3 days | , –3 days |
| Production | 7– , 5 days | 7– , 5 days |
| Quality inspection | , –2 days | , –2 days |
| Labeling & packaging | , –3 days | , –3 days |
| Freight transit | 25–35 days | 5– , , days |
| Customs clearance | 2–5 days | , –3 days |
| FBA receiving | 2–5 days | 2–5 days |
| Total lead time | 39–68 days | , 9–4 , days |
How to Reduce Lead Time
- Maintain standing orders: Keep your supplier producing continuously — they’ll prioritize your orders.
- Pre-order packaging materials: Have cartons, poly bags, and labels ready before production finishes.
- Use air freight for urgent restocks: Cuts 2
,
–3
,
days off lead time.
- Use a China warehouse: Store finished products at your forwarder’s warehouse in China, ready to ship when needed.
- Pre-clear customs: Provide documents early for pre-clearance processing.
Seasonal Replenishment Strategy
Amazon Seasonal Calendar
| Season | Peak Period | When to Ship | Recommended Method |
| Q4 Holiday | Nov , –Dec 25 | By Aug , 5 | Sea freight (ship by July) |
| Prime Day | July (mid-month) | By May , 5 | Sea freight (ship by April) |
| Back to School | Aug , –Sep , 5 | By June , | Sea freight (ship by May) |
| Spring Sale | March–April | By Jan , 5 | Sea freight (ship by Dec) |
| Chinese New Year | Jan/Feb (factory closure) | Stock up before CNY | Sea freight + air freight |
Seasonal Stock-Up Strategy
For Q4 (the biggest sales season):
| Timeline | Action |
| June | Forecast Q4 demand (2–3x normal volume) |
| July | Place production order with supplier |
| August | Ship by sea freight (must leave China by Aug , 5) |
| September | Shipment in transit; prepare PPC campaigns |
| October | Shipment arrives at FBA; inventory goes live |
| November | Peak sales begin; monitor inventory daily |
| December | Last-minute air freight if running low |
FAQ
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