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How does MerchantSpring calculate inventory days cover?

Days cover estimates how long current usable inventory can support forecast demand.

Inventory days cover estimates how many days current stock may last based on forecast demand.

How is days cover calculated?

The calculation is:

Days cover = total usable inventory ÷ forecast weighted daily sales

For example:

  • Usable inventory: 52 units
  • Forecast weighted daily sales: 1.7 units per day
  • Days cover: approximately 30 days

This means the available supply is expected to support roughly 30 days of demand if the forecast sales rate continues.

What is included in the inventory input?

The supply picture may include relevant inventory across Amazon’s fulfilment network, including FBA and Amazon Warehousing and Distribution stock.

However, inventory statuses represent different levels of availability:

  • FBA Available is ready to fulfil customer orders.
  • Reserved and FC Transfer stock is within Amazon’s network but may not be immediately available.
  • FBA or AWD Inbound represents future supply that has not completed receiving.
  • Unfulfillable inventory should not be treated as dependable supply.

The inventory included in the calculation should therefore be reviewed alongside its status and expected availability.

How is forecast daily sales calculated?

Forecast weighted daily sales can combine average sales rates from different recent periods, such as:

  • The last 7 days
  • The last 30 days
  • The last 60 days

Each period can be given a different weighting.

Giving more weight to recent sales makes the forecast respond more quickly to current demand. Giving more weight to a longer period creates a steadier forecast that is less affected by short-term changes.

How should days cover be interpreted?

Days cover should be considered alongside:

  • Supplier order lead time
  • Target days cover
  • Demand volatility
  • Upcoming promotions
  • Seasonal sales patterns
  • Current inbound inventory
  • The speed and reliability of replenishment

For example, 30 days of cover may be sufficient for a product that can be replenished quickly, but it may create a stockout risk where the supplier lead time is several months.

Why can days cover change?

The result can change when:

  • Available or inbound inventory changes
  • Sales increase or decrease
  • Forecast weights are updated
  • Inventory moves between Amazon statuses
  • A shipment is received or delayed
  • The selected account, store, ASIN or reporting scope changes
Important note

Days cover is a planning estimate, not a guarantee. Promotions, seasonality, stockouts and sudden changes in demand can affect both the forecast and the actual time inventory lasts.

Need help?

Contact support@merchantspring.io and include the relevant account, marketplace, store, ASIN, reporting period, forecast settings and any helpful screenshots or exports.