Stock on order forgotten
A shipment in transit already covers the gap it was ordered for. Comparing the shelf rather than the stock position against the trigger produces a second order nobody needs, and the cash for it leaves immediately.
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Reorder point calculator
The stock level that should trigger the next purchase order, built from your own sales pace, your supplier's real lead time and a safety stock you choose. At 14 units a day from a 21-day supplier with 4 days of safety, the trigger is 350 units.
Reorder when stock falls to
748units
Lead time demand
570
sold while you wait
Safety stock
178
14 days of cover
Order now
1.468
units, to hit target cover
Demand and supply
What you hold, and what you are aiming at
↑ ↓ to nudge, Shift for ten. Commas or dots both work.
This product
Sold per day−12,67
Lead time demand570
Safety stock178
Reorder point748
Stock position today420
Order value−€28.112,20
Safety cover is held in days rather than derived from a service level on purpose: a number you chose because your supplier is occasionally two weeks late is easier to defend, and easier to revise, than one produced by a statistical assumption about demand that nobody in the building can check.
You are at 420 including stock on order, so the order is already due: about 1.468 units, €28.112,20 at landed cost.
Watch cover and velocity per SKU
An estimate from flat rates. In nouz every order is priced from the costs of its own day.
What this calculator does
What it does
A reorder point calculator works out the stock level at which a purchase order has to go out: the units that sell during the supplier's real lead time, plus a safety stock you choose. At 14 units a day from a 21-day supplier with 4 days of safety, that is 350 units. It also sizes the order.
The formula
A number to watch, instead of a shelf to check.
A reorder point converts “we should probably order more” into a threshold: the units that will sell while the supplier is preparing and shipping, plus a cushion for the weeks when either demand or the supplier misbehaves. Cross it, and the order goes out that day.
The stock position, not the shelf, is what crosses it. Units already on order are stock you have, just not yet: forgetting them is the classic double-order that turns a cash-flow problem into a warehouse problem.
The safety stock is held in days, a cushion you can defend because the supplier was two weeks late twice this year. To size it from a service level or by the max-demand method instead, the safety stock calculator works it out both ways and gives the answer in days to bring back here.
Worked example
Why the lead time your supplier quotes is too short
A quoted lead time usually ends when the goods leave the factory or reach the port. Your stock has to last until they are saleable, and freight, customs, inspection, the receiving dock and putaway all come after the quoted date.
Take a supplier quoting 30 days whose goods then spend 10 days at the port and 3 in the warehouse: the stock lives through 43. At 12,67 units a day, those 13 days are what the quoted figure leaves out.
Ordered on the quoted lead time, every order goes out 165 units too late: the safety stock is spent covering a delay that was never a surprise, and the next late shipment empties the shelf.
Measure what the last few orders really took from purchase order to saleable shelf, and plan on the slowest of them when the supplier is erratic.
Where it goes wrong
Four ways a reorder point fires at the wrong moment.
Two of these order too late and two order too much, and all four are ordinary.
The contractual lead time
Use what the last few orders actually took, door to saleable shelf, including customs, quality checks and putaway. The agreed lead time is a plan; the observed one is what your stock has to survive.
Ordering exactly to the target cover
Units keep selling while the shipment is in transit, so an order sized only for the target arrives already behind. Covering the target plus the lead time is what stops a store reordering again a fortnight after a delivery lands.
Safety stock everywhere, equally
A reliable supplier and a steady product need almost no cushion; a seasonal product from a distant supplier needs a large one. A blanket safety policy overstocks half the catalogue to protect the other half.
Worked example
A 45-day supplier and a fortnight of nerves
The calculator’s defaults: 380 units sold in 30 days, a 45-day lead time, 14 days of safety stock, 420 units on hand and nothing on order, aiming at 90 days of cover at a €19,15 landed cost.
At 12,67 units a day, 570 units sell during the lead time and 178 units are the safety stock.
The trigger is 748 units and the position is 420 units, so the order is overdue rather than upcoming. Ordering 1.468 units brings the store to 90 days of cover after the shipment lands, and consumes €28.112 of cash to do it.
That last figure is the reason reorder points and cash planning are one conversation: a correct order can still be an unaffordable one, and finding that out at the trigger is far better than finding it out at the invoice.
In nouz
The same rule, for every product at once.
The reorder planner on Insights, Inventory in nouz runs this calculation for every variant you sell, each on its own pace: its recent weeks and, once it has a year of sales, the same weeks last year.
It dates the day the stock on hand and on its way runs out at that pace, and the day to order by, one lead time earlier, so the reorder lands as the last unit sells. Stock on its way counts as arriving in time, since Shopify gives no arrival date. The suggested order covers the lead time plus 60 days of sales, priced at today’s unit cost.
The lead time is the store’s, set on the Products page, and a product with a supplier of its own keeps its own. The planner holds no safety stock: order your cushion’s days before its Order by date, which is what the safety days above add to the trigger.
In the app
nouz works this out from every order, every day.
A calculator works from flat rates you type once. nouz prices every single order from the cost rules that were in force on that order's own date, and rebuilds the same statement every night from your own orders and your own ad spend.
- Every cost at the rate of its own day. Product costs, parcels and payment fees per order, so a price change never rewrites last month.
- Ad spend comes in by itself. Meta, Google and TikTok through their official APIs, plus anything you add by hand or by CSV.
- The same lines, per product. What is left after product costs, after shipping and payment fees, and after ads, for every product you sell.
What is a reorder point?
The stock level at which you place the next order, so the delivery arrives before the shelf empties. It is the demand during the lead time plus a safety cushion: at 12,67 units a day, a 45-day lead time and 14 days of safety, the trigger is 748 units rather than a round number somebody picked.
How much safety stock should I hold?
Enough to cover how late your supplier actually is and how much demand actually varies, both of which you can observe. Held in days of cover it stays honest and revisable: a supplier that has been two weeks late twice this year justifies two weeks, and a reliable one does not. The safety stock calculator sizes it both ways the textbooks teach and turns either answer into days.
Why is the lead time my supplier quotes too short?
Because it usually ends when the goods leave the factory or reach the port, and your stock has to last until they are saleable. Freight, customs, inspection, the receiving dock and putaway all come after the quoted date. Use what the last few orders really took from purchase order to shelf, and plan on the slowest of them when the supplier is erratic.
Does stock already on order count?
Yes, and forgetting it is the classic double-order. What matters is the stock position, on hand plus on order, against the reorder point. This calculator uses the position, which is why entering an inbound shipment can turn an apparently urgent order into one that is weeks away.
How many units should I actually order?
Enough to reach your target cover once the delivery lands, which means covering the lead time as well as the target. Ordering exactly to target ignores the units that sell while the shipment is in transit, and is how stores end up reordering again the week after a delivery arrives.
Does nouz work out reorder points for me?
Yes, as a date for every variant rather than a level. The reorder planner on Insights, Inventory sets each variant's Order by day one lead time before its stock on hand and on its way runs out at the expected pace, and suggests an order that covers the lead time plus 60 days of sales, priced at today's unit cost. It holds no safety stock of its own: this calculator does the same arithmetic for one product and adds the cushion.
More calculators
Four that go with this one.
Each one is a different question about the same statement. All 32 are free, and none of them asks you to sign up.
All calculatorsSafety stock calculator
The spare stock that covers a late supplier or a busy week, by service level or by max demand, in units and in days.L17COGSL18COGS %Stock coverage calculator
How many days the stock on hand will last, and whether that survives your supplier's lead time.L17COGSL18COGS %Inventory turnover calculator
How many times a year your stock turns into sales, and how long a unit sits before it does.L17COGSL18COGS %Landed cost calculator
What a unit really costs to own once freight, duty, currency and shrinkage are on it.L17COGSL18COGS %L19CM1
The terms this calculator uses
- Reorder pointThe stock level that should trigger a purchase order.
- Lead timeOrder placed to stock saleable, as observed.
- Safety stockThe cushion held against demand and suppliers going wrong.
- StockoutDemand arriving at an empty shelf.
- BackorderSelling what you do not yet have.
- Stock coverageHow many days the stock you hold will last.
- Inventory forecastingWhen each product runs out, and what to reorder.
- Demand planningTurning expected sales into what to order, and when.
The long version
Want the long version rather than the arithmetic?
Profit on paper€9.500and the account can still fall12 min readProfitable on paper, no cash in the bank: the four calendarsThe statement says the store earns money and the account still falls. The four calendars that separate profit from cash, and the plan that fits a genuinely profitable store.Profitable on paper, no cash in the bankA reorder date for every product, from your real orders.
The reorder planner in nouz tells you when each product runs out at its own pace, what to order and by when, and what it costs, from your own sales, your stock in Shopify and the lead times you set.
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