This reorder point calculator takes how fast a SKU sells, how long your supplier takes, and how much cushion you want, and returns the stock level at which to place the next order. Runs in your browser. Nothing is sent anywhere; your entries are remembered only in this browser.
Reorder Point Calculator
A planning starting point; widen the safety buffer for variable lead times.
Forvendo · every other Friday
One operating decision, worked through with numbers
The same approach this calculator takes: the sources named, the assumptions shown, and the arithmetic left where you can check it.
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The formula behind this reorder point calculator
A reorder point is the inventory level at which a replenishment order needs to go out so that stock arrives before it runs out.
Reorder point = daily sales velocity × (lead time in days + safety buffer in days)
The first part of that bracket is what you will sell while you wait. The second is what protects you when either the selling or the waiting goes wrong.
The buffer is entered in days of cover, not units. Three days of buffer on a SKU selling 8 a day is 24 units; on a SKU selling 1 a day it is 3. Expressing it in days keeps the cushion proportional to how fast the item actually moves, which is what you want when one buffer setting has to work across a catalog.
Getting the three inputs right
- Daily sales velocity. Units per day for that SKU, from a trailing window that reflects current demand. A 30-day window is responsive; a 90-day window is stable. Seasonal SKUs need the window that matches the season you are ordering into, not the one you just left.
- Lead time. Not the supplier’s quoted production time. The clock starts when you send the purchase order and stops when the stock is sellable on your shelf, which includes payment clearing, production, freight, customs, and receiving.
- Safety buffer, in days. Extra days of cover for when demand spikes or the shipment slips. Setting it to zero means a reorder point that is correct only when nothing goes wrong.
Why the lead time number is usually too low
The single most common error is using the quoted production time as the lead time. A supplier saying “14 days” often means 14 days of production after payment clears, which is not the same as 14 days from the moment you decide to reorder.
The practical fix is to measure it once from your own records: the date you sent the last PO, and the date that stock was actually sellable. That gap is your real lead time, and it is frequently 1.5 to 2 times the quoted figure.
What a reorder point does not solve
- How much to order. The reorder point tells you when. Order quantity is a separate decision involving unit economics, minimum order quantities, and cash.
- Cash timing. A mathematically correct reorder point can still be unaffordable in the week it triggers.
- Demand that is changing shape. The formula assumes velocity is roughly stable across the lead time. For a SKU trending sharply up or down, recalculate more often than you reorder.
Related
- Reorder Point SOP for Solo Shopify Stores — the full method, including how to set safety stock without tying up cash
- All free calculators
- Free spreadsheets and templates
Frequently asked questions
How do you calculate a reorder point?
Multiply daily sales velocity by the sum of lead time and your safety buffer, both in days. The calculator above returns that figure, rounded up to whole units.
How much safety stock should a small store hold?
Enough to cover the variability you actually experience, which is a function of how unreliable your supplier is and how spiky your demand is. A stable supplier and flat demand need very little; a slipping supplier and a SKU with promotional spikes need considerably more.
Does Shopify calculate reorder points?
Shopify tracks inventory levels and can alert on low stock at a threshold you set manually — see Managing inventory in the Shopify Help Center — but it does not derive that threshold from your velocity and lead time. This calculator produces the number to put in.
Are my numbers saved anywhere?
Nothing is sent anywhere. The number fields are remembered in this browser only, so the figures are still there next visit.