1. Definition

Overstock means having more inventory than the expected or actual demand.
It’s the opposite of stockout — too much stock sitting in the warehouse.

The Overstock % metric measures how much excess inventory you have compared to optimal demand/stock level.

2. Formula (common versions)

  • Relative to Demand:

$\text{Overstock \%} = \frac{\text{Inventory on hand – Actual Demand}}{\text{Actual Demand}} \times 100$

  • Relative to Target Stock Level:

$\text{Overstock \%} = \frac{\text{Inventory on hand – Target Inventory}}{\text{Target Inventory}} \times 100$

3. Causes of Overstock

  • Over-forecasting demand (predicting higher demand than actual).
  • Supplier constraints (minimum order quantities, bulk deals).
  • Slow-moving SKUs (poor product selection or low popularity).
  • Seasonality mismanagement (e.g., leftover winter coats in spring).
  • Long lead times → buying too early.

4. Consequences of Overstock

  • Holding Costs: Storage, insurance, taxes.
  • Capital Tie-up: Cash stuck in unsold inventory.
  • Obsolescence: Tech products, fashion, perishables lose value.
  • Discounting & Waste: Forced markdowns, spoilage.

5. Example

  • Demand forecast: 1,000 units.
  • Actual demand: 800 units.
  • Inventory on hand: 1,200 units.

Excess stock = 1,200 – 800 = 400 units.

$\text{Overstock \%} = \frac{400}{800} \times 100 = 50\%$

That means inventory is 50% higher than what was needed.

Summary

  • Overstock % shows the level of excess inventory.
  • Too much stock → high holding costs, waste, and lost capital efficiency.
  • Balanced with Stockout % to measure supply chain efficiency.