Free tool
Reorder Point Calculator
Set a replenishment trigger around lead time and your chosen buffer.
This reorder point calculator works out the units needed to cover demand while you wait for replenishment, plus the buffer you choose. It gives you a clear trigger to compare with a consistently defined inventory position.
The result does not set the size of the next purchase order. Order quantity also depends on buying rules, minimums, available cash and the stock you want after receipt. Use Weeks of Supply to inspect current cover and the Inventory Cash Planner to check payment timing. The Inventory Planning Calculator adds context for reviewing the broader stock position.
Unit demand · Lead time in days · User-chosen buffer
Demand and lead time
Use a consistent scope and cost basis for every figure.
The example is illustrative. Replace it with your own figures; results update as you type. Your entries stay in this page until you choose to copy them.
Need help finding your figures in Shopify?
Copy an input checklist for Sidekick. Store reports may not contain every cost or scenario assumption; verify the source and mark missing figures rather than guessing.
User-chosen buffer
Inventory position
How this tool works
How the reorder point is calculated
Multiply daily unit demand by replenishment lead time in days. Add the buffer units you choose to obtain the reorder point. If the buffer is entered in days, convert those days to units using the same daily demand rate. A fractional unit threshold is rounded up where whole items are required.
Compare the trigger with an inventory position that consistently accounts for stock on hand, confirmed incoming stock and outstanding commitments. Do not count the same reservation or backorder twice. The buffer is an explicit planning choice; this calculation does not estimate a statistical service level or an optimal safety stock.
Reorder point = daily unit demand × lead time in days + chosen buffer units, rounded up to whole units.
A trigger for a three-week lead time
At 10 units of daily demand and a 21-day lead time, expected lead-time demand is 210 units. Add a chosen buffer of 70 units for a reorder point of 280. Reaching that inventory position is a signal to review replenishment, not an instruction to order 280 units.
Your full calculation
| Measure | Result · USD |
|---|---|
| Reorder point, rounded upInventory position is above the reorder trigger. | 380 |
| Expected demand during lead time | 280 |
| User-chosen buffer units | 100 |
| Inventory positionOn hand + confirmed on order − committed/backordered units. | 400 |
| Position above or below trigger | 20 |
| On-hand units | 250 |
| Confirmed on-order units | 200 |
| Committed or backordered units | 50 |
Questions & answers
Understanding your result
How is ROP calculated?
Multiply average daily unit demand by lead time in days, then add the buffer units selected. For example, 8 units per day over 15 days plus a 40-unit buffer gives a reorder point of 160 units.
Is reorder point the same as order quantity?
No. Reorder point is the inventory threshold that triggers a replenishment decision. Order quantity is how much you buy. The latter depends on your target position, existing pipeline, supplier minimums, cash and other buying constraints.
How should I choose safety stock for this calculator?
Enter a buffer based on the demand and lead-time uncertainty you want to allow for. The calculator uses your chosen units or days; it does not derive a service-level-based safety stock from statistical demand and lead-time variation.
Which stock figure should I compare with the trigger?
Use a consistent inventory position, usually stock on hand plus confirmed on-order units less unfilled commitments. Check receipt timing and avoid subtracting commitments twice. Late incoming stock may leave a gap even when the total pipeline looks sufficient.