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Home / Glossary / Days of inventory

Replenishment

Days of inventory

Inventory expressed as days of sales — a turnover-style view of stock.

Definition

Days of inventory (DOI / DSI) expresses how many days stock would last at recent sales, or how many days of COGS sit in inventory. Ecommerce ops teams usually mean on-hand ÷ daily units; finance may use (average inventory ÷ COGS) × period days.

Formula

Ops view: DOI = on-hand units ÷ average daily units sold
Finance view: DOI = (average inventory value ÷ COGS) × days in period

Worked example

On hand 1,200 units, 40 sold/day → 30 DOI. If that is above your target band, you are overstocked on that SKU.

Why it matters for replenishment

DOI spots ageing cash traps early and pairs with sell-through when reviewing a season or PO.

Guides & calculators

Related terms

Common questions

Units or value?

Ops usually use units; finance uses value and COGS. Say which you mean.

Is higher DOI always bad?

Not for long-lead imports you intentionally pre-build. It is bad when sell-through stalls.

How does DOI relate to turnover?

Inventory turnover ≈ period days ÷ DOI (finance view).

Is days of inventory the same everywhere?

The idea is shared, but formulas and marketplace rules differ. Use the definition on this page for ecommerce replenishment.

Do I need software to track days of inventory?

A spreadsheet works for a few SKUs. Once you have many suppliers or channels, a replenishment tool keeps the numbers current.

Does OmniRestock change my live stock?

Not unless you switch Stock write or Purchase orders on for a connection. Drafts stay drafts until you confirm.

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