WOC (Weeks of Cover)
Weeks of Cover measures how long current stock will last at the present rate of sale: units on hand divided by weekly sales. The answer is a runway expressed in weeks, which is exactly how inventory decisions are actually made.
What is WOC?
Weeks of Cover measures how long current stock will last at the present rate of sale: units on hand divided by weekly sales. The answer is a runway expressed in weeks, which is exactly how inventory decisions are actually made.
It is the bridge between inventory and demand. Everything else in replenishment — order quantities, lead times, safety stock — only means something once translated into how long the stock will last, and this is the translation.
Reading the runway
Three interpretations. A low figure means stock will run out before replenishment arrives if the lead time exceeds it. A high figure means capital is tied up in inventory that is selling slowly, with storage costs accruing against it. And the ideal figure is not a number but a relationship: cover should exceed lead time by enough margin to absorb demand variability, and no more.
It is also the most useful metric for comparing products to each other, because it normalises for size. Two products, one selling a hundred units a week and one selling five, cannot be compared on absolute stock — but their weeks of cover are directly comparable, and a divergence between them usually points at a planning error rather than a demand difference.
Using it to plan
Three practices. Set cover targets by product class rather than globally, since a fast-moving consumable and a slow-moving durable need different margins over lead time. Review it on a regular rhythm, because the figure changes every time the sales rate moves — and a healthy figure can become a shortage within a fortnight if demand accelerates. And combine it with lead time to decide the order point: the moment cover falls below the time needed to replenish is the moment the order should already have been placed.
The most common planning failure is treating the figure as a target to reach rather than a signal to read. Cover of six weeks is good news for a product with a two-week lead time and a warning for one that takes eight weeks to restock.
In practice
A brand sets cover targets by product class, reviews them weekly against lead times, and places orders when cover approaches the replenishment interval rather than when stock runs low. Shortages and overstock both fall, and the capital released from the slow lines funds deeper cover on the fast ones.
How Harpy Media helps
Inventory planning is part of our operations work: cover compared against real lead times, targets set by class, and order points triggered by the relationship between the two.
WOC FAQ
What is Weeks of Cover?
A forward-looking inventory measure: units on hand divided by average weekly sales, expressing how long current stock will last before replenishment is needed.
What is a good figure?
It depends on lead time. Cover should comfortably exceed the time needed to replenish, with enough margin for demand variability — and no more than that.
Why compare it with lead time?
Because the two together tell you whether to act. Cover below lead time means a stockout is already in progress, however healthy the absolute number looks.
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