Max demand during lead time
352 units
Free calculator
Type your maximum and average daily sales and lead time. Safety stock updates live. No email, no gate, nothing leaves this page.
The calculator
The boxes start filled with an illustrative example, not a benchmark. Replace it with your own numbers.
Your busiest normal day, not a once-a-year outlier.
The longest this supplier has taken, not the number on the purchase order.
Safety stock
Carry 172 extra units as a buffer beyond your average lead-time demand, enough to cover a lead time that runs long or a stretch of higher-than-average daily sales.
max demand during lead time = max daily sales * max lead time average demand during lead time = average daily sales * average lead time safety stock = max demand during lead time - average demand during lead time extra days of cover = safety stock / average daily sales
This is the classic max-minus-average method, a real, named, transparent simplification: compare the worst realistic case against the average case, and hold the difference.
See it on your own data Real numbers from your Shopify store, not a guess.
The max-minus-average method above is a real, named, transparent simplification, it is not the only legitimate way to size a buffer. A formal service-level calculation uses demand variability and a chosen stockout-risk tolerance to arrive at a number, and it can land somewhere different from this one.
Treat this as a simpler, more approachable method that's easy to explain and easy to check by hand, not as the single correct answer.
Questions
Extra inventory held beyond what you expect to sell during a normal lead time, as a buffer against demand or lead time running higher than usual. It's what keeps a busy week or a late shipment from turning into a stockout.
You can, and larger operations sometimes do. A service-level or standard-deviation-based approach models demand variability more precisely and lets you target a specific stockout-risk tolerance. The max-minus-average method here is simpler and more transparent, easy to compute by hand and easy to explain to someone else. Both are legitimate; they trade off precision against simplicity differently.
Both directions have a real cost. Too low and a busy week or late shipment turns into a stockout and a lost sale. Too high and cash sits in inventory that isn't moving, along with the storage cost of holding it. Neither failure mode is free.
Directly, it's one of the two inputs. Reorder point is lead-time demand plus safety stock, so the number calculated above plugs straight into the reorder point calculator.
Only indirectly, through the max lead time input. If a supplier is unreliable, that should already be reflected in a wider gap between your average and max lead time. This calculator doesn't model supplier reliability separately from that.
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Upstream tracks daily sales swings and lead time variability per SKU from your own store data, so safety stock reflects what's actually happening, not a single manually-typed max.