Stock Cover

Stock cover (also called days of cover, inventory cover, weeks of cover, or weeks of supply) is the number of days or weeks that current inventory will last at the current rate of sale before running out. It is the central planning metric in retail merchandise management: too low and the business risks stockouts and lost sales; too high and it accumulates carrying costs, ties up working capital, and risks markdown exposure as seasons end.

Terminology

The concept travels under several names that refer to the same underlying idea — how long current stock will last:

Term	Common context
Stock Cover	UK retail / European retail planning
Days of Cover	Logistics, supply chain, WMS contexts
Weeks of Cover (WOC)	Merchandise planning, buying, WSSI
Weeks of Supply (WOS)	US retail, DTC ecommerce, AI replenishment tools
Days Inventory on Hand (DOH) / Days Sales of Inventory (DSI)	Financial / accounting context
Days Inventory Outstanding (DIO)	Supply chain finance, EazyStock definition

Sources: Mecalux, ShipBob, EazyStock, KPI Examples/Operately, Reactive SDP (all via Web — Stock Cover 2026-07-22)

Formulas

Two parallel formula conventions exist — financial (value-based) and operational (unit-based) — which can produce different signals and should not be mixed without standardisation (ShipBob, Phocas — Web — Stock Cover 2026-07-22).

Financial / accounting formula (DOH):

DOH = (Average Inventory ÷ COGS) × 365 Average Inventory = (Beginning Inventory + Ending Inventory) ÷ 2 — ShipBob, eFulfillmentService (May 2026)

Operational / merchandising formula (WOS):

WOS = Current Inventory Units ÷ Average Weekly Sales Units — WAIR for Retail (Web — Stock Cover 2026-07-22)

Forward-looking variant (FWOS) — preferred for planning:

FWOS = Current Inventory Units ÷ Average Forecasted Weekly Sales — Inventory Planner, Toolio (Web — Stock Cover 2026-07-22)

Full planning formula (Reactive SDP — includes on-order):

WOC = (On Hand + On Order arriving before end of planning horizon) ÷ Forward Weekly Demand — Reactive SDP describes this as the correct formula; the simpler WOS ignores on-order stock already committed, understating cover when intake is en route (Web — Stock Cover 2026-07-22)

Relationship to inventory turns:

Inventory Turns = 365 ÷ DOH (or 52 ÷ WOS) If a business targets 4 inventory turns per year, closing stock should provide ~13 weeks cover (3 months). At 8 turns per year, cover should be ~6.5 weeks (Retail Dogma, 2022)

Retail Dogma turns-to-cover conversion above is from 2022 and may be superseded. The mathematical relationship (Turns = 52 ÷ WOS) is definitional and not time-sensitive; the "3–4 turns = good for fashion" benchmark is the stale element.

Benchmarks (as-of 2026-07-22)

Fashion/apparel benchmark from Onramp Funds is 2025 data. eFulfillmentService is May 2026 — the most current available.

Segment	Days of cover	Implied turns
General ecommerce (all categories)	~45 days	~8×
Fashion & apparel — overall	30–60 days	~6–12×
Fast fashion / value	30–45 days	~8–12×
Mid-market apparel	45–90 days	~4–8×
Luxury / high-end fashion	91–182 days	~2–4×
Wholesale distribution (most common)	61–90 days	~4–6×

Sources: eFulfillmentService (May 2026), Onramp Funds (2025, stale-risk), Phocas 2026 Wholesale Distribution Inventory Trends report — all via Web — Stock Cover 2026-07-22

ShipBob recommends 30–60 days for bestsellers in ecommerce, adjusted for lead time and cash flow — 30 days for top sellers, 14 days for slower-moving items (as-of 2026-07-22).

Lead-time-based targets in fashion retail (as-of 2026-07-22)

StyleMatrix and Reactive SDP are undated vendor/consultancy sources; treat as illustrative rather than verified benchmarks.

Supplier type	Lead time	Target WOC	Reorder trigger
Domestic	1–2 weeks	4–8 weeks	Below 3 weeks
European	3–6 weeks	8–14 weeks	Below 6 weeks; over 20 weeks = over-invested
China / Asia sea freight	16–27 weeks	20–35 weeks	Critical below 18 weeks

Sources: StyleMatrix, Reactive SDP (both undated) — Web — Stock Cover 2026-07-22

Reactive SDP states the minimum WOC floor is: Lead Time + (Lead Time × 25% safety buffer). For an 8-week lead time, minimum target WOC ≈ 10 weeks (Web — Stock Cover 2026-07-22).

Product-type variation

Stock cover targets must differ by item type (Reactive SDP, StyleMatrix, WAIR — Web — Stock Cover 2026-07-22):

Core replenishment (basics, staples): continuous replenishment; WOC tied to lead time + safety buffer; no seasonal end-date constraint
Fashion newness (seasonal buys): WOC must be evaluated against the season-end date, not just lead time — a style going out of season in 8 weeks with 18 weeks of cover will land at clearance unless something changes (Reactive SDP)
Category benchmarks (vendor, undated): fast fashion 4–6 weeks; premium footwear 10–14 weeks (size/style complexity); basics (socks, vests) 3–4 weeks (WAIR, Reactive SDP)

Stock cover within WSSI / OTB

Stock cover is a derived output of WSSI (Weekly Sales, Stock and Intake) and Open-to-Buy (OTB) planning tools. Retail Dogma (2022, stale-risk) describes it as calculated automatically each period inside a WSSI tool: the closing stock at end of each period provides a forward cover figure, which planners compare against lead time to assess whether a reorder is needed. This is the primary mechanism by which cover targets translate into intake decisions (Retail Dogma — Web — Stock Cover 2026-07-22).

Cost of distortion (as-of 2026)

Getting stock cover wrong in either direction carries large costs:

Global inventory distortion (stockouts + overstock combined): above $1.7 trillion (XoroSoft, 2026)
Stockouts alone: $1.2 trillion in lost retail sales globally; $144.9 billion in North America (XoroSoft, 2026)
Carrying costs for excess inventory: 20–30% of inventory value per year (AisleStock, 2026)
55% of SMBs held at least 20% excess stock, 46% reported at least 5% dead stock (Supply Chain Planning Benchmark, cited by AisleStock 2026)
Fashion industry (2024): estimated 2.5B–5B items of excess stock worth up to $140B in sales; inventory distortion costing retailers 20–30% of potential revenue (Business of Fashion, State of Fashion 2025 — stale-risk)

Sources: Web — Stock Cover 2026-07-22

Contradictions

Formula type: ShipBob's DOH uses value-based Average Inventory ÷ COGS as the denominator [shipbob.com/inventory-kpis/inventory-days-on-hand/]. Phocas uses unit-quantity-based Qty On Hand ÷ Monthly Average Qty Sold [phocassoftware.com]. Reactive SDP includes on-order stock in the numerator [reactivesdp.com/blog/weeks-of-cover-retail-planning.html]. These three conventions are structurally equivalent in concept but will produce different outputs if mixed. The financial DOH and the operational WOS are particularly prone to comparison errors.

Cover-target philosophy: WAIR for Retail and Toolio treat weeks of cover as a core planning target to optimise toward [wair.ai / toolio.com]. nVentic argues that cover targets applied at the material-group level are flawed — they mask items that are simultaneously over- and understocked, creating a false sense of balance — and advocates scrapping group-level targets in favour of bottom-up item-level Safety Stock Optimisation [nventic.com/insights/cover-uncovered/].

Benchmark scope: The overall fashion/apparel benchmark of 30–60 days covers the entire segment (Onramp Funds 2025, eFulfillmentService May 2026). Fast fashion WOS targets of 4–6 weeks (~28–42 days) sit inside the low end of this range, while luxury 2–4 turns implies 91–182 days — far above it. The aggregate range blends sub-segments with opposite inventory strategies and should not be used as a single target without segment-level adjustment.

Key terms

Term	Meaning
Forward WOS / FWOS	Current inventory ÷ forecasted weekly sales — preferred over backward-looking average
Days Inventory Outstanding (DIO)	Value-based equivalent of WOS; used in supply-chain finance reporting
Inventory turns	52 ÷ WOS (or 365 ÷ DOH); the inverse metric, common in financial reporting
Carrying cost	Cost of holding inventory (storage, insurance, obsolescence, capital) — typically 20–30% of value/year
Stockout	Cover reaches zero; demand cannot be fulfilled from on-hand stock
Dead stock	Inventory with zero or near-zero sell rate; days of cover approaches infinity
Season-end date constraint	The date by which fashion-newness items must be sold at full price; creates an absolute WOC ceiling