What Is a Slow-Moving SKU in FBA?
A slow-moving SKU is a product in your catalog that consistently sells at a velocity below the catalog average and below the threshold where storage costs and opportunity cost stay comfortably below contribution margin. Unlike dead stock, a slow-moving SKU still generates regular sales; it just generates fewer of them per dollar of inventory invested.
The standard benchmarks for identifying a slow-moving SKU on Amazon FBA:
- 90-day sell-through rate below 30%: Less than a third of stocked inventory sells in a quarter.
- Annual inventory turnover below 3x: Capital cycles less than three times per year.
- Days of supply consistently above 120: Current inventory would last more than four months at current sales velocity.
A slow-moving SKU is not automatically a problem. Some are profitable per unit and round out a catalog strategically. The question is whether each one earns its FBA shelf space relative to alternatives. This is where systematic SKU rationalization matters: you need to evaluate slow-movers individually rather than treat them as a single block.
Velocity Benchmarks for a Slow-Moving SKU
Three formulas help you classify whether a SKU qualifies as slow-moving:
Sell-Through Rate (90-day) = Units Sold (90d) / (Units Sold + Average Units On Hand) x 100
Inventory Turnover (annual) = COGS (12 months) / Average Inventory Value
Days of Supply = Current Units On Hand / Average Daily Sales
| Tier | 90-day STR | Annual Turnover | Days of Supply | Action |
|---|---|---|---|---|
| Healthy | > 50% | > 6x | < 60 | Maintain |
| Watch | 30-50% | 3-6x | 60-120 | Monitor closely |
| Slow-moving | 15-30% | 1.5-3x | 120-240 | Intervene |
| Critical | < 15% | < 1.5x | > 240 | Rationalize or remove |
Worked Example: Evaluating a Slow-Moving SKU
A $55 ASP product, 60-day lead time, selling 8 units per month. Current inventory: 110 units in FBA. Cubic feet per unit: 0.18. Contribution margin: 32% ($17.60/unit).
Velocity calculations:
- Average daily sales: 8/30 = 0.27 units/day
- Days of supply: 110/0.27 = 408 days
- 90-day sell-through: 24 / (24 + 110) = 17.9%
- Annual turnover: ($55 x 8 x 12) / ($55 x 110) = 0.87x
This SKU lands solidly in slow-moving territory bordering on critical.
Cost calculations:
- Monthly storage: 110 units x 0.18 cu ft x $0.87 = $17.23/month (Jan-Sep) or $47.52/month (Oct-Dec)
- Aged surcharge starts at day 181: at current velocity, 65+ units will trigger surcharges within 6 months
- Monthly gross profit: 8 units x $17.60 = $140.80
Storage as % of gross profit: $17.23 / $140.80 = 12.2% (acceptable Jan-Sep) | $47.52 / $140.80 = 33.7% (Q4 warning zone)
Decision framework: Stop reordering for 4 months to draw inventory down to ~80 days of supply. Once at healthier levels, reduce future order quantities by 50% to match actual velocity. If margin compresses or storage costs rise, escalate to rationalization.
Why Slow-Moving SKUs Are More Costly in FBA
FBA's fee structure makes slow-moving inventory expensive in ways traditional retail does not face:
- Compounding storage fees: $0.87/cu ft monthly during Jan-Sep, jumping to $2.40/cu ft in Q4. Slow-movers that arrive in summer get hit with the Q4 multiplier before they sell through.
- Aged inventory surcharge: Kicks in at day 181 ($1.50/cu ft) and escalates rapidly to $6.90+/cu ft after 365 days. A slow-moving SKU that sits 200+ days starts paying double rent.
- IPI score drag: Excess inventory percentage and low sell-through both pull IPI down. Lower IPI means lower storage limits, which constrains your ability to stock A-tier products.
- Restock limit consumption: Every cubic foot of slow-moving inventory is a cubic foot unavailable for higher-velocity SKUs.
The cost of holding slow-movers is rarely visible in your day-to-day P&L because storage fees deduct from settlement transfers in small increments. But over 12 months, a catalog with 30% slow-movers can lose 5-8% of gross profit to storage costs alone.
Common Slow-Moving SKU Mistakes
1. Treating all slow-movers the same way. A slow-mover with 35% margin and steady sell-through is fundamentally different from one with 8% margin and declining velocity. The first is worth keeping with tighter reorder quantities. The second is a removal candidate. Run the per-SKU economics; do not paint with a broad brush.
2. Ignoring seasonal patterns. A pool float looks slow-moving in February. So does a Christmas decoration in July. Compare a SKU's velocity against the same period last year, not against the catalog average. Tag seasonal items so off-season velocity does not trigger false rationalization.
3. Sending in large replenishment quantities for slow-movers. Some sellers reorder slow-movers in supplier-MOQ quantities (1,000 units when the SKU sells 8/month) to save on per-unit cost. The savings on COGS get wiped out by 6-12 months of storage fees plus aged surcharges. Smaller, more frequent orders almost always win for slow-movers.
Related Glossary Terms
Frequently Asked Questions
At what sell-through rate is a SKU considered slow-moving?
A 90-day sell-through rate below 30% is the typical threshold. Below 20% indicates a clear slow-mover that needs intervention. The exact threshold depends on your category and storage cost structure, but anything below 30% means inventory is sitting longer than it should.
Should I remove slow-moving inventory from FBA?
Not necessarily. Many slow-movers are profitable per unit. The decision depends on whether monthly storage cost plus opportunity cost exceeds margin contribution. If a slow-moving SKU's storage fees consume more than 25% of its monthly gross profit, consider removal or transition to FBM.
How do slow-moving SKUs affect my IPI score?
Slow-moving SKUs drag IPI down through the excess inventory and sell-through rate sub-scores. They tie up storage capacity without generating proportional revenue, which Amazon penalizes. A catalog full of slow-movers can push IPI below the threshold for restock limit increases.
What is the difference between a slow-moving SKU and dead stock?
Slow-moving SKUs still sell, just at a lower rate than the catalog average. Dead stock has zero or near-zero sales over an extended period (typically 90+ days). A slow-mover might sell 8 units per month; dead stock might sell 1 unit per quarter. The intervention strategies differ accordingly.
How do I avoid creating more slow-moving inventory?
Order in smaller quantities for SKUs already showing slow movement signs. Use accurate demand forecasting rather than supplier MOQ as the basis for reorder size. Run quarterly SKU rationalization reviews. Tighten safety stock levels for low-velocity products.