#1006 · E-commerce Tool

Amazon Inventory Calculator

Estimate when to reorder Amazon inventory and whether your current stock level is balanced, at risk of stockout, or likely to create excess storage costs.

Calculator

Amazon seller inputs
units
units/day
days
units
Ad space

How to use this calculator

Enter current inventory, average daily sales, supplier lead time, and safety stock. The calculator estimates days of supply, reorder point, and stockout risk.

What the result means

Balanced inventory protects ranking and sales without tying up too much cash in slow-moving stock. Too little inventory risks stockouts; too much creates storage and cash-flow pressure.

Days of supply = Current inventory ÷ Average daily sales. Reorder point = Daily sales × Lead time + Safety stock.

Use recent 30-day sales for normal demand and adjust daily sales upward before peak seasons.

Example calculation

With 600 units, 12 daily sales, 20-day lead time, and 80 safety units, supply lasts 50 days and reorder point is 320 units.

Tips for better results

  • Reorder before inventory reaches the reorder point.
  • Increase safety stock before seasonal spikes.
  • Avoid holding more than 120 days of slow-moving stock.
  • Track supplier lead time changes.
  • Use removal or discount plans for excess inventory.

FAQ

How many days of inventory should Amazon sellers keep?

Many sellers target 45 to 90 days of supply, but the right level depends on lead time, sales volatility, cash flow, and storage fees.

When should I reorder Amazon FBA inventory?

Reorder when inventory approaches lead-time demand plus safety stock, not when inventory is nearly sold out.

What is a good inventory turnover for Amazon sellers?

A healthy turnover varies by category, but faster-moving products often turn several times per year without repeated stockouts.

How do I avoid Amazon stockouts?

Track days of supply, supplier lead time, inbound shipments, safety stock, and seasonal demand changes before inventory becomes urgent.

How can I reduce Amazon storage fees?

Improve sell-through, reduce over-ordering, remove stale inventory, run promotions, and avoid sending excessive slow-moving units to FBA.

Amazon inventory module

MetricMeaning
Days of supplyHow long current units can support demand.
Reorder pointInventory level where replenishment should begin.
Stockout dateEstimated date when inventory reaches zero.
Health scoreScore based on whether supply is balanced.

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