Calculate when to reorder inventory based on demand and lead time. Includes safety stock integration and multi-SKU support.
Try an example:
Formula:
Reorder Point = (Daily Demand x Lead Time) + Safety Stock
Enter demand and lead time to calculate reorder point.
3 days
Range: 1-5 days
7 days
Range: 5-14 days
30 days
Range: 14-45 days
14 days
Range: 7-30 days
5 days
Range: 3-10 days
2 days
Range: 1-3 days
Source: APICS (Association for Supply Chain Management) and ASCM Supply Chain Operations Reference
The reorder point (ROP) is the inventory level that triggers a new purchase order to replenish stock. It ensures you place orders early enough to receive new inventory before running out, accounting for lead time and demand uncertainty.
The basic formula is straightforward: Reorder Point = (Average Daily Demand x Lead Time) + Safety Stock. However, determining the right safety stock requires understanding your demand variability and desired service level.
Getting the reorder point right is critical. Too high, and you carry excess inventory with increased holding costs. Too low, and you risk stockouts that can damage customer relationships and revenue. The goal is finding the optimal balance across your operations tools.
For comprehensive inventory management guidance, refer to APICS Body of Knowledge and Investopedia's reorder point guide.
Review your sales or usage data over a representative period (ideally 30-90 days). Divide total units sold by number of days. For seasonal products, use data from the relevant season.
Example: 1,500 units sold in 30 days = 50 units/day average demand
Track the time from when you place an order until inventory is received and ready for sale. Include supplier processing time, shipping, receiving, and any quality inspection time.
Example: 2 days supplier processing + 5 days shipping + 1 day receiving = 8 days lead time
Safety stock protects against demand spikes and supply delays. Use the formula: Safety Stock = Z-score x Standard Deviation x Square Root of Lead Time. The Z-score corresponds to your desired service level (1.65 for 95%, 2.33 for 99%).
Example: 1.65 x 10 units std dev x sqrt(8) = 47 units safety stock
Multiply average daily demand by lead time, then add safety stock. This is the inventory level at which you should place a new order.
Example:
Demand During Lead Time: 50 units/day x 8 days = 400 units
Safety Stock: 47 units
Reorder Point: 400 + 47 = 447 units
Pair this tool with the COGS Calculator and the Efficiency Calculator to cross-check inputs. For strategic context, read our founder's LOI negotiation guide and explore the Operations & Inventory tools hub.
Reorder point determines WHEN to order. It is the inventory level that triggers a purchase order, ensuring you receive new stock before running out.
Safety stock protects against uncertainty. Both demand variability and lead time uncertainty should be factored into your safety stock level calculation.
Lead time reduction lowers inventory needs. Shorter lead times mean lower reorder points and less capital tied up in inventory. Track inventory turnover to confirm that lower reorder points are not causing stockouts.
Service level impacts cost. Higher service levels (99% vs 95%) require significantly more safety stock. Balance customer service with carrying costs.
Review and adjust regularly. Demand patterns change seasonally and over time. Review reorder points at least quarterly to maintain optimal levels. For practical inventory checklists, browse the Valuefy blog.
The reorder point (ROP) is the inventory level at which a new order should be placed to replenish stock before it runs out. It accounts for the time it takes to receive new inventory (lead time) and provides a buffer (safety stock) against demand variability. The formula is: Reorder Point = (Average Daily Demand x Lead Time) + Safety Stock.
Safety stock can be calculated using the formula: Safety Stock = Z-score x Standard Deviation of Demand x Square Root of Lead Time. The Z-score corresponds to your desired service level (e.g., 1.65 for 95%, 2.33 for 99%). A simpler method is to use a fixed percentage of demand during lead time, typically 20-50% depending on demand variability.
Service level depends on the criticality of the item. Critical items like medical supplies should target 99%+. High-value items that drive significant revenue should aim for 97%. Standard inventory typically uses 95%. Low-priority or easily substitutable items may use 90% or lower to reduce carrying costs.
Longer lead times require higher reorder points because more inventory is needed to cover demand while waiting for replenishment. If lead time doubles, the demand during lead time component of your reorder point also doubles. Reducing supplier lead times is one of the most effective ways to lower inventory investment.
The reorder point tells you WHEN to order, while the reorder quantity (often calculated using Economic Order Quantity or EOQ) tells you HOW MUCH to order. When stock hits the reorder point, you place an order for the reorder quantity. Both are essential components of an inventory management system.
Demand variability is addressed through safety stock. Calculate the standard deviation of your daily demand over a representative period (ideally 30-90 days). Higher variability requires more safety stock. Also consider seasonal patterns separately, as they represent predictable changes rather than random variability.
Yes, each product should have its own reorder point based on its unique demand pattern, lead time, and criticality. ABC analysis can help prioritize: A items (high value, tight control), B items (moderate control), and C items (simpler rules). This calculator supports multiple SKUs for this reason.
Review reorder points quarterly at minimum, or monthly for items with volatile demand. Major changes in demand patterns, supplier lead times, or business strategy should trigger immediate review. Many modern inventory systems calculate dynamic reorder points that adjust automatically based on recent data.
Four primary factors determine your reorder point: (1) Average daily demand — the mean number of units sold or consumed per day, typically calculated from 30–90 days of sales history; (2) Lead time — the number of days between placing an order and receiving stock, which varies from 1–3 days for local suppliers to 30–60 days for overseas manufacturers; (3) Demand variability — the standard deviation of daily demand, which determines how much safety stock is needed; and (4) Service level — the probability of avoiding a stockout, commonly set at 95% for standard SKUs and 99%+ for critical items. Increasing any of these four factors raises your reorder point and requires more inventory investment. Businesses that reduce supplier lead time by 50% can often cut their reorder points by a similar proportion, directly freeing working capital.
Seasonal products require a dynamic reorder point that changes throughout the year rather than a fixed value. During peak season, average daily demand is higher, so both the demand-during-lead-time component and the required safety stock increase. In the off-season, a lower reorder point prevents overstocking and reduces carrying costs. To handle seasonality: calculate separate reorder points for each season using demand data from equivalent periods in prior years, apply a demand multiplier based on seasonal index, and consider extending lead times for seasonal peaks if suppliers face capacity constraints. Many businesses set 3–4 distinct reorder point profiles per SKU — pre-season build-up, peak, wind-down, and off-season — and switch between them on a calendar schedule.