Replenishment

How many days of stock should you hold

The number falls out of how long your goods take to arrive, which is why the figure that keeps a domestic seller lean would empty an importer's shelves.

Marcus VolstedCo-founder, Restocio Published 10 September 2026Updated 10 September 20268 min read

The days of stock you should hold is your delivery time, plus a cushion for that delivery running late, plus however long you want a single order to last. It is not a benchmark you can borrow from another store. A supplier who ships in a week and a factory that puts goods on a boat give answers that differ by more than a factor of ten, and the second answer means placing the order while the shelf still looks completely full.

What does days of stock actually mean?

Units on hand divided by units sold per day, calculated per variant. Ninety units is three months of cover for something selling one a day and four days for something selling twenty, which is why a unit count settles nothing.

The divisor is where this quietly goes wrong. Count the days the product was genuinely on the shelf rather than the days on the calendar, or everything that has ever run out reads as a slow mover. That correction is written up beside a reorder point calculator that applies it. Take it as given here.

Shopify will not show you the figure. Its own documentation, read on 10 September 2026, defines inventory as "the number of each product variant that you have available to sell". Units, split by location, with no view of how fast they are leaving or how long the next lot takes to arrive.

Worth clearing up the name too. If searching for days to cover brought you here from something about short selling, that is FINRA's measure, short interest divided by average daily share volume, read on 10 September 2026. Same words, nothing to do with your shelf.

How many days of stock should you hold?

Three separate jobs hide inside the one number, and each is set by something different.

Part	The job it does	What sets it	Our default for a sea importer
Pipeline days	Covers demand while the order is being made and shipped	Your measured lead time, all of it	70 for the boat, plus the supplier's production days
Cushion days	Absorbs a late boat or a fortnight of unusually strong sales	How unreliable the route and the demand actually are	60
Cycle days	Decides how long one order lasts before the next one	How often you want to place orders	30

Add the first two together and you have the level at which the order has to go in. That is the number worth putting on a screen, because it is the only one with a date attached. The cushion doubles as your floor, the stock still there on the day the delivery lands.

Only the third part is a free choice. Longer cycles mean fewer, larger orders and more money standing still. Shorter cycles free that cash and cost you more shipments. Which way to push it when cash is the constraint is a separate argument.

Why does an importer hold ten times what a domestic seller holds?

Because most of an importer's days of stock is not a buffer at all. It is the journey.

	Supplier who ships in a week	Importer on a 70 day boat
Pipeline days	7	70, plus production if goods are made to order
Cushion days	A few	60 on our defaults
You order when stock reaches	About 10 days of cover	About 130 days of cover
What the shelf looks like that day	Nearly empty	Four months full
Being a week late costs	A week of the same freight	Air freight, several times the price per kilo

Read the first row rather than the total. Seventy of those 130 days are money on a ship, and with goods made to order most of the number is capital that has left your bank and become nothing sellable yet. Trimming days of stock to look lean cuts into the part that was never optional.

One store-wide figure is wrong for the same reason. Two products selling at identical rates need different levels if one ships from finished stock and the other from a factory that starts cutting fabric when your deposit clears. Delivery time is set per freight mode in our app and production days sit on the supplier, so the made-to-order product gets the longer trigger without anyone deciding it. The five segments that belong in a lead time are in the lead time guide.

What does this look like inside the app?

The field in Settings called Days of stock is only the cycle part. It sets how many days each order should cover going forward. Directly beneath it sits "Delivery time to include in every order", which is added to it, and the two together decide how big an order gets. Left at zero, that second field sizes orders as though goods arrive the instant you press buy, so a new install starts on the slowest route you have switched on.

Separate arithmetic drives the trigger, and that is the one to watch. Days of stock remaining, minus the sea lead time, minus the cushion, minus the supplier's production days, gives the days left before the order has to go in. On our defaults it fires at 130 days of cover, and the order is sized so the shelf is back at that level the day the boat docks.

That cushion moved from 30 days to 60 on 2 September 2026, which sounds like timidity and is really about freight. Order while your days of stock is still above the sea lead time and the whole order fits on the boat. Slip below it and the arithmetic has to buy a faster shipment to bridge the gap until the boat lands, which is the expensive half of every late decision.

Restocio computes days of stock per SKU, summed across that SKU’s active variants, and measures the sales rate over days the product was recorded in stock rather than days elapsed. It then shows the order deadline as a countdown instead of a stock level. The whole loop it sits inside is in the Shopify replenishment guide.

What happens when the number is set too low?

A quiet and very specific failure. If the days each order covers, plus the delivery time you typed, comes to less than the slowest route you actually use, the order is empty before it lands. Not occasionally. Every cycle, by construction. An order covering 30 days that takes 70 days to arrive has run out 40 days before the container reaches the port.

Nothing looks broken while this happens. Orders go in on time, the supplier ships on time, the shelf goes dark anyway, and the obvious conclusion is that demand grew. Our settings screen flags that combination as critical and names the gap in days rather than sizing the order quietly, because it is not a preference to respect. It is arithmetic that cannot work.

Can you hold too many days of stock?

Easily, and it is the same number read from the other end. A product showing 400 days of cover is not well stocked, it is a purchasing decision worth revisiting, and the aging bands are worth knowing before it gets there.

The two errors are not symmetrical, though. Holding too many days costs money you get back on the next cycle. Holding too few costs sales that never come back. Where you have to guess, guess long.

Where this number stops being useful

Days of stock assumes today's pace holds, and for anything seasonal that assumption expires on a known date. Ninety days of cover in September can be thirty days of cover in November, and nothing will warn you, because a trailing rate has no idea what month it is about to be.

Two honest limits in our own version. The cushion is still one flat number for the whole store rather than one per product, so the steady seller and the erratic one both get 60 days, which is too generous for one and too thin for the other. We compute the per-product figure from each product's own demand variability and show it as advice beside the field, but it steers no recommendation until the founders sign it off. And the cycle length stays your choice, because working it out properly needs your fixed cost per order, which we do not collect and will not invent for you.

Common questions

How many days of stock should I hold?

Delivery time plus a cushion for that delivery being late, plus however long you want one order to last. A supplier who ships in a week and keeps three cushion days means ordering at about 10 days of cover. An importer on a 70 day boat with a 60 day cushion orders at about 130 days of cover, which is our default, and that order goes in while the shelf still looks full.

Is days of stock the same as days to cover?

No, and the collision is why this question is hard to search. In inventory, days of stock is units on hand divided by units sold per day. In finance, FINRA defines days to cover as short interest divided by average daily share volume, meaning the days of trading it would take to buy back shares sold short. Same words, unrelated measures.

How do you calculate days of stock?

Divide units on hand by units sold per day, per variant rather than per product. Count the daily rate over the days the product was actually in stock, not days elapsed, or anything that has run out before will look slower than it is and you will order too little of it.

Should every product have the same days of stock?

No. The figure is driven by lead time, so a product from a supplier holding finished goods needs far less cover than an identical product from a factory that only starts making it when you order. Production days and freight route both belong in the calculation, and they differ per supplier and per shipping mode.

Is 30 days of stock enough?

Only if your goods arrive in well under 30 days. If the delivery takes 70 days, an order sized to cover 30 days runs out 40 days before it lands, every single cycle, no matter how punctual your supplier is. Compare the days you plan to hold against the slowest route you actually use before comparing it against anything else.

Does Shopify show days of stock?

No. Shopify tracks the number of each variant available to sell, by location, and reports on what sold. It has no concept of supplier lead time, so it cannot convert a unit count into days of cover or into an order deadline. That conversion is done outside Shopify, usually in a spreadsheet or a purchasing app.

Marcus Volsted

Co-founder, Restocio

Marcus co-founded Restocio and works on it daily with a Swedish importer who plans their purchasing in it every working day. Restocio is built in Sweden by two founders, one Swedish and one Danish, and Marcus is the Danish one. Most of the examples on this blog come from that store's real ordering decisions rather than from a textbook. Why we are building it.