TL;DR
Inventory Performance Index (IPI) is Amazon's 0-1000 score that measures how efficiently you manage FBA inventory across four metrics: excess inventory, sell-through, stranded inventory, and in-stock rate. Below the threshold (currently 400), Amazon caps your storage capacity.

Definition

The Inventory Performance Index is the score Amazon uses to decide how much storage capacity your account gets in FBA fulfillment centers. It rolls up four behaviors into a single number that updates weekly: how much excess inventory you’re carrying, how fast it’s selling through, whether listings have FBA stock attached but no buy box, and what percentage of your active SKUs have inventory available.

Amazon publishes the score in Seller Central under Inventory > FBA Inventory > Inventory Performance. The threshold has moved over the years (350, then 400, then 450 for some accounts, then back to 400). As of April 2026, sellers below 400 get capacity restrictions on standard-size storage. Sellers above 400 typically get unlimited storage, though Amazon still applies aged inventory surcharges separately.

The score is not published as an exact formula. Amazon describes the four components qualitatively. From observed seller data, sell-through rate and excess inventory each move the needle the most. Stranded inventory and in-stock rate matter at the edges.

How Amazon calculates IPI

FORMULA
IPI = weighted function of four inputs:
• Excess inventory %  (units > 90 days supply)
• Sell-through rate  (units shipped / avg units in stock, trailing 90 days)
• Stranded inventory %  (FBA listings with stock but no buy box)
• In-stock rate  (active SKUs with inventory / total active SKUs)
// Score range: 0–1000
// Threshold for unlimited capacity (April 2026): 400

Worked example: a $2.1M private label seller

A private label seller running 18 SKUs at $2.1M annual revenue (average selling price $34, average lead time 75 days from China) checks IPI on April 15, 2026:

  • 4 SKUs are sitting on 142 days of supply (excess inventory)
  • Trailing 90-day sell-through is 5.8 (units shipped per average unit on hand)
  • 2 SKUs are stranded after recent listing suppressions
  • 16 of 18 active SKUs have inventory available (in-stock rate 89%)

Their score: 437. Above the 400 threshold but with capacity headroom getting tight. If excess inventory creeps another 10%, they’re under threshold by Memorial Day.

The fix: pull excess inventory off Amazon (AWD or 3PL), unstrand the two suppressed listings, and tighten reorder timing on the remaining 16 SKUs. Two weeks of work moves the score to 540 and adds roughly 18% more storage capacity heading into Q4.

Why IPI matters for FBA sellers

IPI is distinct from FBA fee profitability. A SKU with strong IPI contribution can still be unprofitable after fulfillment fees, referral fees, and ad spend. The score tells Amazon you’re a good warehouse tenant. It does not tell you whether a product is making money.

The score also lags. New SKUs do not have enough sell-through history to score well, so launching three new products in a quarter can drag IPI down for 90+ days even if those products sell through quickly. If your account sits near the threshold, plan launches around the score window or absorb the temporary drag in your reorder math.

Common mistakes

  1. Treating IPI as a profitability metric. It measures storage efficiency, not margin. A high-IPI catalog can still bleed cash through fees and ad spend.
  2. Ignoring stranded inventory. Two stranded SKUs can knock 30+ points off the score. Check Seller Central > Inventory > Manage Stranded Inventory weekly.
  3. Reacting to weekly score changes. IPI updates each Monday but reflects trailing 90-day behavior. One week of bad data will not change the trend, and chasing the weekly number leads to over-corrections.

Related terms

Where this shows up in Profit Hawk
Profit Hawk surfaces all four IPI inputs alongside your live score, then shows which SKUs are pushing the number down. The show me the math view spells out exactly how a 90-day sell-through change would shift your score before you act on a recommendation. Start a free trial.
SI Term Stranded inventory › RL Term Restock limits › AWD Term Amazon Warehousing and Distribution › ROP Term Reorder point › PG Pillar guide Reorder point formula in plain language ›

Frequently asked questions

What IPI score do I need to avoid restock limits in 2026?

400 as of April 2026. Amazon has changed the threshold before and may again. Check Seller Central > Inventory > Inventory Performance for the live number on your account, since some accounts have seen the threshold drop to 350 or rise to 450 during specific periods.

How often does IPI update?

Weekly, every Monday. The score reflects the trailing 90 days of activity, so the weekly delta is small unless something material changed (a stuck listing, a reorder that doubled your on-hand).

Does IPI affect my profitability?

Indirectly. Restock limits force tighter buying, which causes stockouts and lost sales. A low IPI also signals that you are consuming warehouse space inefficiently, which correlates with higher long-term storage fees on aged inventory.

Can I influence IPI quickly?

Stranded inventory fixes show up within a week. Sell-through rate and excess inventory take 30 to 60 days to move meaningfully because they use 90-day rolling windows.

Is IPI the same as my Account Health score?

No. Account Health measures policy compliance (late shipments, valid tracking, customer complaints). IPI measures inventory efficiency. Both matter but for different reasons.
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