Inventory Reorder Point and Safety Stock Calculator

Method and assumptions

Reorder point = daily demand × lead days + user-entered safety stock. Inventory position = usable on-hand units + confirmed inbound units. Suggested order = max(0, daily demand × (lead days + target cover days) + buffer − inventory position), rounded up to a whole unit. With zero demand and no stock, cover is shown as “No demand”; zero demand with positive stock is rejected because a days-of-cover ratio has no finite denominator.

Worked example

At 8 units/day with a 6-day lead and a 15-unit buffer, the reorder point is 63 units. Forty units on hand plus 10 inbound gives position 50, or 6.25 days of cover. A 10-day post-lead target suggests ordering 93 units.

How to use the result

Place or review an order when inventory position reaches the reorder point. Because the buffer is entered directly, choose it from your own variability and service needs; this result does not validate supplier reliability or forecast demand.

Input meanings and limits

• Average units used or sold per day: Use your own planning average.
• Supplier lead time: Calendar days from order to usable receipt.
• Chosen safety-stock buffer (units): A user-specified quantity, not a z-score calculation.
• Usable units currently on hand: Exclude damaged or committed units.
• Confirmed inbound units: Only include orders you expect to receive.
• Target days of stock after lead time: Used only for the suggested order quantity.

Inputs accept finite, nonnegative values in the displayed ranges; percentages are bounded to 0–100% (with 99.99% maximum where division by the remaining share is used), and whole-unit or month fields require integers. Currency figures are shown in USD for convenience; enter values in one consistent currency. This is a planning worksheet, not financial, legal, tax, or accounting advice.

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Economic order quantity calculator and Purchase order landed cost calculator.