TL;DR
Weeks of supply is the average number of weeks of forward sales currently held in inventory — calculated as inventory units divided by weekly sales velocity. It is the same metric as <a href="/glossary/inventory-days-on-hand" class="text-brand-600 underline decoration-brand-200 underline-offset-2 hover:text-brand-700">inventory days on hand</a> expressed in weeks. For apparel and seasonal goods, healthy weeks-of-supply is 12–18; for fast-moving consumables, 6–10. Weeks-of-supply is the standard retail and wholesale planning unit.
What is weeks of supply?
Weeks of supply (often abbreviated 'WOS') is the number of weeks of forward sales that current inventory will cover at recent velocity. It is mathematically identical to inventory days on hand divided by 7 — same metric, different unit.
Operators in apparel, seasonal goods, and wholesale-driven categories prefer WOS over DOH because their planning cycles are weekly and their lead times are weeks-long. Operators in fast-moving consumables and subscription D2C prefer DOH because their velocity is daily.
How to calculate it
Weeks of Supply = (current inventory units) / (average weekly sales velocity) Where average weekly sales velocity = (units sold over trailing N weeks) / N Recommended N: 4 weeks for stable seasons, 2 weeks for fast-moving or new launches.
Benchmarks
| Category | Healthy WOS | Caution | Critical |
|---|---|---|---|
| Apparel — in-season | 8–14 | <6 or >16 | <4 or >20 |
| Apparel — full-line | 12–18 | <8 or >22 | <6 or >26 |
| Hard goods | 16–24 | <12 or >30 | <8 or >36 |
| D2C consumables | 6–10 | <4 or >12 | <3 or >16 |
WOS vs DOH — when to use which
WOS and DOH are the same metric, but the operating context determines which unit is clearer:
- Use WOS when: planning cycle is weekly (apparel, seasonal categories), purchase orders are placed weekly, lead times are measured in weeks, the team's reporting cadence is weekly.
- Use DOH when: velocity is daily (fast-moving consumables, subscription D2C), purchase orders are continuous, lead times are short, the team's reporting cadence is daily.
Common pitfalls
- 1. Brand-level WOS for SKU-level decisions. The brand average can sit at a healthy 14 weeks while bottom-quartile SKUs are at 60+ weeks (markdown-bound) and top-quartile SKUs are at 4 weeks (stockout-bound). SKU-level WOS is the only actionable view.
- 2. Confusing on-hand WOS with on-hand-plus-in-transit WOS. The right number depends on the question. Fulfilment availability uses on-hand only. Purchase-order timing uses on-hand + in-transit. Mixing them produces over- or under-ordering.
- 3. Static WOS targets across the season. Healthy WOS at the start of a season is different from healthy WOS in week 8 or week 12. Seasonal targets should glide downward as the season ages — high WOS in week 12 means certain markdown.
Related concepts
Inventory days on hand is the same metric in days. Sell-through rate is the realisation-side complement. Stockout rate and markdown rate are the downside risks of WOS being too low or too high.
At a glance
- Category
- Operations / Cash
- Related
- 5 terms
Frequently asked questions
Should you use WOS or DOH?
Same metric — pick the unit that matches your operating cadence. Weekly planning cycles use WOS. Daily velocity categories use DOH. Some teams use both, reporting WOS for purchasing and DOH for fulfilment availability.
What's a healthy WOS?
Apparel in-season: 8–14 weeks. Apparel full-line: 12–18 weeks. Hard goods: 16–24 weeks. Consumables: 6–10 weeks. The right target = replenishment lead time + safety stock + forecast-error buffer. Anything beyond that is working-capital waste.
How does WOS change across a season?
Healthy WOS should glide downward as a season ages. A SKU at 16 WOS in week 1 is appropriate; the same SKU at 16 WOS in week 12 is markdown-bound. Targets should track season-progress, not stay static.
Sources
- NRF retail benchmarks (2024)
- Apparel inventory planning standards (RFA)
- Fairview customer data (D2C, 2025)
Fairview is an operating intelligence platform that tracks SKU-level weeks of supply against season-progressing targets, separating on-hand from in-transit and flagging structural stockout or overstock pathologies before they require last-minute markdown or expedited reorders. Start your free trial →
Siddharth Gangal is the founder of Fairview. He built the season-progressing WOS layer after watching apparel brands hit healthy-looking aggregate WOS numbers in week 8 that masked SKU-level pathologies which forced 30% blanket markdowns in week 14 — pathologies that SKU-level WOS would have flagged six weeks earlier.
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