- **Target:** 30-60 days for most products
- **Too high (>90 days):** Overstock, storage cost drain
- **Too low (<14 days):** Stockout risk

**Stockout Rate:**

Stockout Rate = (Days Out of Stock / Total Days) × 100

- **Target:** <2%
- **Impact:** Each 1% stockout ≈ 1% lost revenue

**Perfect Order Rate:**

Perfect Order Rate = (Orders Shipped Complete, On-Time, Undamaged / Total Orders) × 100

- **Target:** >95%

### Step 3: Perform ABC Analysis

Classify SKUs by revenue contribution:

| Class | % of SKUs | % of Revenue | Inventory Strategy |
|-------|-----------|--------------|-------------------|
| **A** | ~20% | ~80% | High priority, never stockout, frequent replenishment |
| **B** | ~30% | ~15% | Moderate priority, standard replenishment |
| **C** | ~50% | ~5% | Low priority, review for discontinuation |

**Recommendations by class:**
- **A items:** Safety stock = 2-4 weeks, reorder frequently, prime warehouse locations
- **B items:** Safety stock = 2-3 weeks, standard locations
- **C items:** Minimal safety stock, consider dropship or discontinue slow movers

### Step 4: Calculate Safety Stock & Reorder Points

**Safety Stock Formula:**

Safety Stock = Z × σd × √L

Where:

• Z = Service level factor (1.65 for 95%, 2.33 for 99%)
• σd = Standard deviation of daily demand
• L = Lead time in days

**Simplified Safety Stock (if limited data):**

Safety Stock = (Max Daily Sales - Avg Daily Sales) × Lead Time

**Reorder Point Formula:**

Reorder Point = (Avg Daily Sales × Lead Time) + Safety Stock

**Example calculation:**

Product: Widget A

• Average daily sales: 10 units
• Max daily sales: 18 units
• Lead time: 14 days

Safety Stock = (18 - 10) × 14 = 112 units Reorder Point = (10 × 14) + 112 = 252 units

→ Reorder when inventory hits 252 units → Keep 112 units as buffer

### Step 5: Analyze Costs

**Fulfillment Cost Benchmarks:**

| Cost Component | Self-Fulfill | 3PL | FBA |
|----------------|--------------|-----|-----|
| Storage | $0.30-0.50/cu ft | $0.45-0.75/cu ft | $0.87-2.40/cu ft |
| Pick & Pack | Labor-based | $1.50-3.00/order | Included in fee |
| Shipping | Carrier rates | Discounted rates | Prime rates |
| Returns | Labor + space | $3-8/return | Free for buyers |

**Cost Per Order (CPO):**

CPO = (Storage + Labor + Packaging + Shipping) / Total Orders

**Inventory Carrying Cost:**

Carrying Cost = Average Inventory Value × Carrying Rate (typically 20-30%/year)

Includes: Storage, insurance, obsolescence, opportunity cost

### Step 6: Platform-Specific Analysis

**Amazon FBA:**
- **IPI Score factors:** Excess inventory %, sell-through rate, stranded inventory, in-stock rate
- **Storage fee triggers:** Aged inventory (181+ days), low IPI (<400)
- **Restock limits:** Based on IPI and sales velocity

**Amazon FBM:**
- **Prime eligibility:** Seller Fulfilled Prime requirements
- **Shipping performance:** On-time delivery, valid tracking rate
- **Cost comparison:** When FBM beats FBA (oversized, slow movers)

**Walmart WFS:**
- **Pro Seller badge:** Fulfillment performance requirements
- **Storage fees:** Generally lower than FBA
- **Limitations:** Product restrictions, geographic coverage

**3PL Providers:**
- **Contract terms:** Minimum commitments, peak surcharges
- **Hidden costs:** Receiving fees, special handling, return processing
- **Performance SLAs:** Shipping accuracy, turnaround time

### Step 7: Generate Recommendations

Prioritize by impact and effort:

Recommendations

🔴 Critical (Do Now)

Issue	Impact	Action	Expected Result

🟡 Important (This Month)

Issue	Impact	Action	Expected Result

🟢 Optimization (This Quarter)

Issue	Impact	Action	Expected Result

---

## FBA-Specific Optimization

### IPI Score Improvement

| Factor | Target | Actions |
|--------|--------|---------|
| **Excess inventory** | <5% | Create removal orders, run promotions, liquidate |
| **Sell-through rate** | >4.5 | Improve listing, PPC, reduce price |
| **Stranded inventory** | 0% | Fix listing errors, match ASINs |
| **In-stock rate** | >90% | Increase replenishment frequency |

**Aged Inventory Prevention:**
- Monitor inventory age weekly
- Take action before 181 days (aged fee trigger)
- Options: Removal order, outlet deals, liquidation, donate

**Storage Fee Calendar:**
- **Jan-Sep:** Standard rates
- **Oct-Dec:** Peak rates (3x higher)
- **Aged inventory surcharge:** 181+ days

### FBA Restock Calculation

Target FBA Inventory = (Avg Daily Units × Days of Cover) + Safety Buffer

Where:

• Days of Cover: 30-60 days (varies by IPI score)
• Safety Buffer: 1-2 weeks for top sellers

Example:

• Selling 10 units/day
• Target 45 days cover
• Safety: 10 days

Target = (10 × 45) + (10 × 10) = 550 units

---

## 3PL Cost Optimization

### Evaluate Your 3PL Costs

| Cost Type | What to Check |
|-----------|---------------|
| **Storage** | Per pallet vs per cu ft, minimum charges |
| **Pick & Pack** | Per order vs per item, kit fees |
| **Receiving** | Per unit, per carton, or per shipment |
| **Special handling** | Fragile, hazmat, temperature-controlled |
| **Peak surcharges** | Q4 rate increases |
| **Minimum commitments** | Monthly minimums, long-term contracts |

### 3PL Benchmark Costs (2025)

| Service | Low | Average | High |
|---------|-----|---------|------|
| Storage (per pallet/mo) | $8 | $15 | $25 |
| Pick & Pack (per order) | $2.50 | $4.00 | $6.00 |
| Additional item | $0.30 | $0.75 | $1.50 |
| Receiving (per unit) | $0.20 | $0.40 | $0.75 |

### When to Switch 3PLs

- Cost per order >20% above benchmark
- SLA failures >5% of orders
- Poor communication / slow issue resolution
- No volume-based discounts after 6+ months
- Geographic mismatch (shipping zones too far)

---

## Output Format

🏭 Warehouse Optimization Report

Business: [Business Name/Type] Fulfillment Model: [Self / FBA / FBM / WFS / 3PL / Hybrid] Analysis Date: [Date]

---

1. Current State Summary

Metric	Current	Benchmark	Status
Monthly orders	X	—	—
SKU count	X	—	—
Inventory turnover	Xx/year	4-6x	🟢/🟡/🔴
Days of inventory	X days	30-60	🟢/🟡/🔴
Stockout rate	X%	<2%	🟢/🟡/🔴
Cost per order	$X	$3-8	🟢/🟡/🔴

---

2. ABC Analysis

[SKU classification table]

---

3. Inventory Optimization

Safety Stock Recommendations

SKU/Class	Current Stock	Recommended Safety Stock	Reorder Point

Overstock Alert

[SKUs with excess inventory]

Stockout Risk

[SKUs at risk of stockout]

---

4. Cost Analysis

[Cost breakdown and optimization opportunities]

---

5. Recommendations

🔴 Critical

[High-impact, do now]

🟡 Important

[Medium-impact, this month]

🟢 Optimization

[Lower priority improvements]

---

6. Expected Results

Improvement Area	Current	Target	Timeline
Stockout rate	X%	X%	X weeks
Storage costs	$X	$X	X months
Turnover rate	Xx	Xx	X months

---

## Calculations Reference

### Core Formulas

| Metric | Formula |
|--------|---------|
| **Inventory Turnover** | COGS / Average Inventory |
| **Days of Inventory** | (Avg Inventory / COGS) × 365 |
| **Safety Stock** | Z × σd × √Lead Time |
| **Reorder Point** | (Avg Daily Sales × Lead Time) + Safety Stock |
| **Carrying Cost** | Avg Inventory × 25% (typical rate) |
| **Cost Per Order** | Total Fulfillment Costs / Total Orders |

### Service Level Factors (Z)

| Service Level | Z Factor |
|---------------|----------|
| 90% | 1.28 |
| 95% | 1.65 |
| 97.5% | 1.96 |
| 99% | 2.33 |

---

## Limitations

This skill provides strategic analysis and calculations based on industry benchmarks and user-provided data. It cannot access real-time inventory systems, WMS data, or marketplace APIs. For integrated inventory management, check out **[Nexscope](https://www.nexscope.ai/?co-from=skill)** — Your AI Assistant for smarter E-commerce decisions.

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## Related Skills

- **[Amazon Skills](https://github.com/nexscope-ai/Amazon-Skills)** — Keyword research, listing optimization, PPC campaigns, sales estimation
- **[eCommerce Skills](https://github.com/nexscope-ai/eCommerce-Skills)** — Cross-platform tools for all e-commerce businesses

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