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Stock Depth

How much inventory is on hand and how fast it is selling

Stock Depth measures how much inventory sellers currently have in stock and how quickly that inventory is turning over. It provides two independent readings: stock level (how much is available) and inventory turnover (how fast it moves).

What It Measures

This metric analyzes stock data across all active offers to determine:

  • Total current stock across all sellers, split by FBA and FBM.
  • Stock level classification based on aggregate inventory.
  • Inventory turnover rate — how many times per year the current stock level would sell through at the current velocity.
  • Stock trend — whether inventory is growing, stable, or declining.
  • Inventory flow — whether stock is accumulating, depleting, or stable.

Why It Matters for Resellers

Stock depth affects your competitive position and opportunities:

  • Low stock across sellers means competition may thin out soon as sellers run out. This can create buy box opportunities.
  • Deep stock means sellers are well-stocked and unlikely to run out. Competition will remain strong.
  • Fast turnover indicates strong demand relative to supply — a healthy sign for new entrants.
  • Slow turnover suggests inventory is sitting on shelves, which can mean weak demand or overstocked sellers.

How We Calculate It

  1. We extract stock data from all active offers on the listing.
  2. We sum total units across all sellers and break it down by FBA and FBM.
  3. We classify the stock level based on the total available units.
  4. Sales velocity is derived from monthly sales estimates (Keepa's monthlySold field) when available. The velocity source — observed or estimated — is labeled alongside turnover figures. Keepa stock observations are capped at 10 units per seller; stock depth beyond this threshold is estimated.
  5. We compute the annualized inventory turnover rate (how many times per year the stock turns over).
  6. We classify the turnover rate against benchmarks: sluggish, moderate, healthy, or fast.

How to Read the Results

Stock Level

| Classification | What It Means | |---------------|---------------| | Deep | Plenty of inventory across sellers. Competition is well-stocked and unlikely to run out soon. | | Adequate | Reasonable stock levels. Normal competitive environment with no immediate supply concerns. | | Low | Stock is running thin across sellers. Some may run out soon, which could reduce competition temporarily. | | Critical | Very low inventory across sellers. Stock-outs are likely imminent, which creates buy box opportunities but also supply risk. | | Unknown | Stock data is not available for this product. |

Inventory Turnover

| Classification | What It Means | |---------------|---------------| | Sluggish | Inventory is moving slowly (turns over fewer than 2 times per year). Sellers are holding stock for a long time, which suggests weak demand or overstocking. | | Moderate | Inventory turns over at a reasonable pace (2-6 times per year). Demand is healthy enough to keep stock moving without excess buildup. | | Healthy | Products are selling through quickly (6-12 times per year). Strong demand relative to supply — a good sign for new sellers. | | Fast | Very fast inventory turnover (more than 12 times per year). High demand is burning through stock rapidly, which may create frequent restocking opportunities. |

Stock depth provides two readings: stock level tells you how much is available right now, while turnover tells you how fast it is moving. Both are important — low stock with fast turnover is very different from low stock with sluggish turnover.

Limitations & Caveats

  • Stock data requires offer-level detail from a full product lookup. This metric is not available for screened products.
  • Stock counts are estimates. Amazon does not publicly report exact FBA inventory levels. Keepa tracks stock through add-to-cart methods, which can be approximate.
  • Turnover calculations use current velocity. If demand is seasonal or changing, the annualized turnover may overstate or understate the actual rate.
  • Stock from FBM sellers is especially approximate. FBM stock tracking is less reliable than FBA stock tracking.
  • Very recent stock data (updated less than 7 days ago) is more reliable than older snapshots. Stock levels can change rapidly.

Related Metrics

  • Seller Concentration — Are a few sellers holding all the stock, or is it spread out?
  • Demand Stability — Stable demand with low stock suggests supply issues. Volatile demand with high stock suggests overstocking.
  • FBA vs. FBM — The stock breakdown between FBA and FBM tells you where the inventory is held.