A reorder point tells you when to consider replenishment. The order quantity tells you how far to restore stock once that trigger is reached. The Reorder Calculator separates those decisions and includes incoming and reserved units in the inventory position.
Set demand, lead time and the buffer
Use average demand of five units daily, supplier lead time seven days and safety stock ten units. Expected demand during lead time is 35 units. Adding the safety buffer gives a trigger of 45 units.
Choose 30 days of coverage after arrival. The target position covers seven lead time days plus those 30 days and the ten unit buffer: 195 units in total. This is a planning target, not a demand forecast supplied by the tool.
Compare the trigger with inventory position
With on hand stock 30, incoming stock zero and reservations zero, inventory position is 30. It has reached the reorder trigger. The suggested quantity is 165 units, taking the position from 30 to the target of 195.
Now add 100 incoming units while keeping everything else the same. Position becomes 130, above the 45 unit trigger. The current suggested order is zero even though position remains 65 units short of the target. The tool waits for the trigger instead of topping up on every small decline.
Incoming units need a realistic arrival assumption
Inventory position counts entered on order stock, but that does not make those units available today. A delayed shipment can still produce a stockout before arrival. Use Stock Runway Calculator to examine current available coverage and the entered lead time separately.
Reserved units reduce the position because those units already have a commitment. Avoid counting the same reservation both as demand already deducted from stock and as another reserved amount.
Whole units and practical supplier constraints
The model rounds unit requirements upward where whole quantities are needed. For daily demand 0.11, seven lead time days, ten safety units and 30 days after arrival, the trigger is 11 and the target is 15. With no inventory position, it suggests 15 units.
Supplier carton sizes, minimum orders and storage capacity still require a final purchase decision. They are not automatically enforced here. Save the demand period and lead time assumption, then review them when actual delivery performance changes. Bulk Purchase Discount Calculator can cost the resulting purchase batch before you commit cash.