Free calculator
Stock coverage calculator
How long what you hold will actually last, in days and weeks, valued at landed cost, and measured against the one thing that decides whether it is enough: your supplier's lead time.
A stock coverage calculator divides the units you hold by how fast they sell to give days and weeks of cover. It values that stock at landed cost and compares the cover with your supplier's lead time, which is the comparison that decides whether an order is already late.
This product
What the cover is worth, and what it has to survive
Cover is only comfortable relative to how long a replacement takes to arrive.
Days of cover
33,2days
The stock runs out 11,8 days before a purchase order placed today could arrive, which is about 150 units of demand with nothing on the shelf.
Velocity
12,67
units a day
Weeks of cover
4,7
at that pace
Stock value
€8.043,00
at landed cost
Cover is a ratio, not a quantity: 400 units is generous on a slow product and a fortnight of panic on a fast one. The only comparison that matters is cover against lead time, which is what the reorder point calculator turns into a decision.
Get cover for every SKU, from real salesThe formula
Units tell you nothing. Days tell you everything
Four hundred units is a comfortable position on one product and a fortnight of panic on another. Converting stock into days of cover makes every SKU comparable, and makes the only question that matters answerable: will this last long enough for a replacement to arrive?
That is why the lead time is an input rather than an afterthought. Cover shorter than the lead time means an order placed today lands after the shelf is empty, so the stockout is already scheduled and the only remaining decision is how much demand falls into the gap.
Stock is valued at landed cost here, never at retail, because inventory is money already spent rather than revenue hoped for. A store with generous cover everywhere is not well run; it is financing its warehouse.
Stock valued at cost is line 17 money that has not yet become a cost, which is exactly what makes it a cash question.
Where it goes wrong
Four ways cover reads better than it is
Cover is a simple ratio with four quietly unreliable inputs.
Velocity measured over the wrong window
Seven days after a campaign flatters nothing and terrifies everyone; a year of history hides a product that has doubled since spring. Thirty to ninety days of recent, ordinary trading is usually the honest middle, and seasonal products need the same season last year rather than last month.
Lead time taken from the contract
The agreed lead time and the observed one are different numbers, and only one of them has ever failed you. Use what the last few purchase orders actually took, including customs and putaway, because the shelf does not care what the contract said.
Stock on hand that is not saleable
Damaged units, customer returns awaiting inspection and stock reserved for a wholesale order are all in the warehouse and none of them can be sold to the next customer. Counting them as cover is how a well-stocked product goes out of stock.
Averages across variants
A product with plenty of cover in three sizes and none in the two that actually sell is out of stock in every way that matters to a customer. Cover belongs at the level people buy at, which is the variant, not the product.
Worked example
420 units against a 45-day supplier
The calculator’s defaults: 420 units on hand, 380 sold in the last 30 days, a landed cost of €19,15 and a supplier who takes 45 days from order to saleable stock.
That is 12,67 units a day, so the stock lasts 33,2 days and the warehouse is holding €8.043 of cost.
An order placed today arrives 11,8 days after the shelf empties, which at this velocity is 150 units of demand with nothing to sell. The reorder was due almost a fortnight ago, and no expediting changes that arithmetic now.
This is why cover is monitored rather than checked: the moment to act was when cover crossed 45 days, not when it looked low. The reorder point calculator turns that into a number to watch.
Questions
Stock coverage, answered
How do I calculate stock coverage?
Divide units on hand by units sold per day. Selling 380 units in 30 days is 12,67 a day, so 420 units is about 33 days of cover. The figure is only as good as the period you measure: too short and one busy week distorts it, too long and a genuine trend disappears into the average.
How many days of cover should I hold?
Enough to outlast your lead time plus a margin for it going wrong. A 45-day supplier and a fortnight of safety means reordering at around 60 days of cover, and holding much beyond that is capital sitting on a shelf rather than prudence.
Why value the cover at cost rather than at retail?
Because stock is money you have already spent, not revenue you might earn. Valuing it at retail flatters the balance sheet and hides the real question, which is how much cash is currently unavailable because it is standing in a warehouse.
What does it mean when cover is shorter than the lead time?
That an order placed today arrives after the shelf is empty, so the stockout is already scheduled. The calculator shows how many units of demand fall into that gap, which is the honest cost of the delay: not a shortage in units but lost orders.
Should slow-moving stock be handled differently?
Yes, and the ratio itself will warn you: a product with a year of cover is not well stocked, it is capital that has stopped working, plus storage and obsolescence. Those SKUs are usually better discounted out than reordered around.
More calculators
Four more, all free, all built on the same statement.
Want the long version rather than the arithmetic? Which products actually make money.
The terms this calculator uses:
Cover for every SKU, from the sales that actually happened
nouz computes velocity, cover and stock value per variant from your own orders and your own costs, so the products drifting toward a stockout surface before they get there.