Inventory Reorder Point CalculatorFree online financial calculator — instant results, no sign-up
Calculate reorder point from constant daily demand, lead time and safety stock.
Estimates only, based on the inputs and assumptions shown. This is not financial, investment, tax, or legal advice. Prices, rates and local rules may change; crypto scenarios do not predict returns. Confirm important decisions with a qualified professional.
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About the Inventory Reorder Point Calculator
The Inventory Reorder Point Calculator calculates when to reorder stock using constant daily demand, supplier lead time, and a fixed safety-stock buffer. It shows both expected demand during replenishment and the stock threshold that triggers a new order. With demand of 40 units/day, a 12-day lead time, and 150 units of safety stock, the reorder point is 630 units.
- Average daily demand (units/day)
- The quantity expected to be used or sold each day, measured in units/day and treated as constant; the default is 40.
- Supplier lead time (days)
- The time from placing an order until replenishment is available for use or sale, measured in days; the default is 12.
- Safety stock (units)
- The extra inventory held as a buffer beyond expected lead-time demand, measured in units; the default is 150.
Formula and method
D_LT = d × L; ROP = D_LT + SS = (d × L) + SS.
- D_LTExpected lead-time demand, in units.
- dAverage daily demand, in units/day.
- LSupplier lead time, in days.
- SSSafety stock, in units.
- ROPReorder point, in units.
Multiply average daily demand by supplier lead time to estimate consumption before replenishment arrives, then add safety stock. Using the defaults, lead-time demand is 40 × 12 = 480 units, and the reorder point is 480 + 150 = 630 units.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Average daily demand40 units/day
- Supplier lead time12 days
- Safety stock150 units
Results
- Lead-time demand480
- Reorder point630
How to use the Inventory Reorder Point Calculator
- 1Enter average daily demand in units/day; the default is 40.
- 2Enter supplier lead time in days; the default is 12, and its day basis should match the demand input.
- 3Enter safety stock in units; the default is 150.
- 4Calculate and review the lead-time demand of 480 units and reorder point of 630 units for the default inputs.
- 5Use the reorder point as a replenishment trigger, accounting for stock already on order and any backorders before placing another order.
Reading your result
Lead-time demand is the expected quantity consumed while waiting for replenishment: 480 units with the defaults. Reorder point adds the safety buffer to that consumption: 630 units with the defaults. In a continuous-review system, reorder when inventory position reaches or falls below this threshold; inventory position is on-hand stock plus stock on order minus backorders. If there are no outstanding orders or backorders, this equals on-hand stock. The reorder point is not the quantity to order.
Limitations
The calculation assumes constant daily demand and a fixed supplier lead time. It accepts safety stock as an input rather than calculating an appropriate buffer or guaranteeing a service level. Demand spikes, supplier delays, seasonality, and stock losses can make the threshold insufficient. Demand and lead time must use a consistent calendar-day or working-day basis, and inputs should be nonnegative. The tool does not calculate order quantity, purchasing costs, minimum order requirements, or additional protection needed when inventory is reviewed only periodically.
Common questions
Why is the reorder point 630 units rather than 480 units?+
The 480 units cover expected demand during the 12-day lead time at 40 units/day. Adding 150 units of safety stock raises the reorder trigger to 630 units.
Does a reorder point of 630 mean I should order 630 units?+
No. It is the inventory threshold for triggering replenishment, not the order quantity. Order size must be determined separately from purchasing constraints, target stock levels, or an order-quantity policy.
Should supplier lead time use working days or calendar days?+
Use the same basis as average daily demand. If 40 units/day represents consumption per calendar day, the 12-day lead time must also represent calendar days; do not mix working-day demand with calendar-day lead time.
Does entering 150 units of safety stock guarantee I will avoid stockouts?+
No. The calculator simply adds the entered buffer to expected lead-time demand. Whether 150 units is sufficient depends on actual demand variation, supplier reliability, and the service level you want to achieve.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
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Results are estimates for informational purposes and are not financial, medical or legal advice.