Knowledge Base

📦 Understanding Amazon Inventory Metrics: IPI, STR, and Sell-Through Explained

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🔍 Overview

Amazon inventory metrics like Inventory Performance Index (IPI), Sell-Through Rate (STR), and Sell-Through directly affect how much inventory you can store, how fast it moves, and how profitable your FBA business is.
This guide explains how these metrics work and how to use them to avoid restrictions and scale with confidence.

👥 Who This Is For

This guide is useful for:

  • 🆕 New Amazon sellers trying to understand inventory limits

  • 📦 FBA sellers managing restocks and aging inventory

  • 📈 Growing brands planning for scale or Q4 demand

  • 🧠 Advanced sellers optimizing cash flow and operational efficiency

🧩 Key Concepts You Need to Know

Before taking action, understand how Amazon evaluates inventory health.

  • 📊 Inventory Performance Index (IPI)
    A composite score Amazon uses to measure how efficiently you manage FBA inventory. It impacts storage and restock limits.

  • 🔄 Sell-Through Rate (STR)
    How quickly inventory sells compared to the average inventory on hand.

  • ⚠️ Excess Inventory
    Units Amazon predicts will not sell in a reasonable timeframe.

  • 🏢 FBA Storage Limits
    The maximum inventory Amazon allows you to store, influenced by your IPI score.

📍 All metrics are found in Seller Central → Inventory → Inventory Performance.

🛠️ Step-by-Step Guide: How to Manage IPI, STR, and Sell-Through

1️⃣ Review Your Inventory Performance Dashboard Weekly

  • Navigate to Seller Central → Inventory → Inventory Performance

  • Monitor:

    • IPI score

    • Sell-Through

    • Excess inventory

    • Stranded inventory

✅ Best Practice: Track trends, not single-week changes
❌ Common Pitfall: Overreacting to short-term dips

💡 Pro Tip: Add a weekly calendar reminder to review inventory health.

2️⃣ Improve Sell-Through by Reducing Overstock

  • Identify SKUs with:

    • Low sales velocity

    • High days of supply

  • Take action:

    • Adjust pricing

    • Add coupons

    • Pause restocks on slow movers

✅ Best Practice: Match inventory levels to real demand
❌ Common Pitfall: Restocking based on hope, not data

💡 Pro Tip: Aim for a Sell-Through Rate above 1.0 for most products.

3️⃣ Remove or Liquidate Excess Inventory Early

  • Review Excess Inventory recommendations

  • Choose:

    • 🚚 Removal orders

    • ♻️ Liquidation

    • 🔖 Aggressive promotions

✅ Best Practice: Act before long-term storage fees hit
❌ Common Pitfall: Waiting for sales that never come

💡 Pro Tip: Small losses now often prevent bigger losses later.

4️⃣ Fix Stranded Inventory Immediately

  • Check the Stranded Inventory report

  • Common causes:

    • Listing errors

    • Suppressed ASINs

    • Missing pricing

✅ Best Practice: Resolve issues within days
❌ Common Pitfall: Ignoring “small” stranded quantities

💡 Pro Tip: Even a few stranded units can hurt your IPI.

5️⃣ Align Restocking with Actual Sales Velocity

  • Base restocks on:

    • 30–60 day sales averages

    • Seasonality trends

  • Avoid bulk shipments without proven demand

✅ Best Practice: Smaller, frequent shipments reduce risk
❌ Common Pitfall: Over-shipping to save on freight

💡 Pro Tip: Amazon rewards consistency more than volume.

🧪 Real-World Examples

📦 Example 1: Small Private Label Seller

  • Seller Type: Beginner FBA seller (2 SKUs)

  • Problem: IPI dropped due to slow-moving inventory

  • Action: Paused restocks, ran coupons, removed excess units

  • Result: IPI recovered in 6 weeks

🏷️ Example 2: Mid-Size Brand Scaling Catalog

  • Seller Type: 7-figure brand with 30+ ASINs

  • Problem: Storage limits blocking launches

  • Action: Reduced depth on low-velocity SKUs

  • Result: Improved sell-through and restock capacity

🚫 Common Mistakes to Avoid

  1. ❌ Chasing the IPI Score Instead of the Drivers
    Sellers fixate on the number, not the causes.
    ✅ Fix inventory health—the score follows.

  2. ❌ Over-Restocking Past Winners
    Yesterday’s demand ≠ today’s demand.
    ✅ Use recent sales data, not historical peaks.

  3. ❌ Waiting Until Amazon Restricts You
    Action often comes too late.
    ✅ Review inventory metrics weekly.

🎯 Expected Results

By applying these practices, sellers can expect:

  • 📈 More stable IPI scores

  • 🚫 Fewer storage and restock restrictions

  • 💰 Lower storage and removal fees

  • 🔄 Faster inventory turnover

  • 📦 More predictable scaling capacity

❓ FAQs

What is a good IPI score?
✅ Generally 400+, with higher scores offering more flexibility.

How often is IPI updated?
🔁 Typically recalculated weekly.

Do ads improve sell-through?
📢 They can help, but won’t fix poor inventory planning.

Does FBM inventory affect IPI?
🚚 No. IPI applies only to FBA inventory.

Is removing inventory bad?
❌ No. Strategic removals often reduce long-term losses.

Use this checklist once per week to review your FBA inventory health, protect your IPI score, and catch issues like excess or stranded inventory before they affect storage limits or fees.