Reorder Point Calculator
Free Reorder point Calculator for operations & inventory. Enter your numbers to see returns, costs, and optimized scenarios instantly.
Reviewed by Sahil, Senior Finance & Tax Editor
Formula
ROP = (Avg Daily Demand x Lead Time) + Safety Stock
The reorder point (ROP) is the sum of average demand during lead time and safety stock. Safety stock uses the statistical formula SS = Z x sqrt(LT x sigma_d^2 + d^2 x sigma_LT^2), where Z is the service level Z-score, LT is lead time, sigma_d is demand standard deviation, d is average demand, and sigma_LT is lead time standard deviation.
Worked Examples
Example 1: Retail Product Reorder Point
Problem:A product sells 50 units daily, lead time is 7 days, demand std dev is 10 units, lead time std dev is 1 day, targeting 95% service level.
Solution:Z-score for 95% = 1.645\nAvg demand during lead time = 50 x 7 = 350 units\nSafety stock = 1.645 x sqrt(7 x 10^2 + 50^2 x 1^2)\n= 1.645 x sqrt(700 + 2500)\n= 1.645 x sqrt(3200)\n= 1.645 x 56.57 = 93 units\nReorder Point = 350 + 93 = 443 units
Result:Reorder Point: 443 units | Safety Stock: 93 units | Lead Time Demand: 350 units
Example 2: EOQ with Inventory Costs
Problem:Annual demand 18,000 units, ordering cost $50/order, unit cost $25, holding cost 20% of unit cost.
Solution:Holding cost per unit = $25 x 0.20 = $5/year\nEOQ = sqrt(2 x 18,000 x 50 / 5)\n= sqrt(360,000)\n= 600 units\nOrders per year = 18,000 / 600 = 30\nAnnual ordering cost = 30 x $50 = $1,500\nAnnual holding cost = (600/2) x $5 = $1,500\nTotal annual cost = $3,000
Result:EOQ: 600 units | 30 orders/year | Total Cost: $3,000/year
Frequently Asked Questions
What is a reorder point and why is it important for inventory management?
A reorder point is the inventory level at which a new purchase order should be placed to replenish stock before it runs out. It accounts for the time between placing an order and receiving it, known as lead time, plus a safety buffer for unexpected demand spikes or delivery delays. Setting accurate reorder points is critical because ordering too late leads to stockouts, lost sales, and dissatisfied customers, while ordering too early ties up capital in excess inventory and increases holding costs. The basic formula is Reorder Point equals Average Daily Demand multiplied by Lead Time in Days plus Safety Stock. Businesses that optimize their reorder points typically reduce stockouts by 30 to 50 percent while simultaneously decreasing excess inventory carrying costs.
What is Economic Order Quantity and how does it relate to reorder points?
Economic Order Quantity, or EOQ, is the optimal order size that minimizes total inventory costs by balancing ordering costs against holding costs. The formula is EOQ equals the square root of two times annual demand times ordering cost per order divided by annual holding cost per unit. EOQ works alongside reorder points to create a complete inventory policy: the reorder point tells you when to order, and EOQ tells you how much to order. Together, they form the fixed-order-quantity model. For example, if your reorder point is 500 units and EOQ is 1,200 units, you place an order for 1,200 units whenever inventory drops to 500. This combination ensures uninterrupted supply while minimizing the total cost of procurement and storage.
How often should I recalculate reorder points and what data do I need?
Reorder points should be recalculated at least quarterly, and monthly for high-velocity or seasonal products. The key data inputs required include average daily demand calculated from at least 30 to 90 days of sales history, standard deviation of daily demand to measure variability, average supplier lead time tracked across multiple orders, and lead time standard deviation to capture delivery reliability. Seasonal businesses should use rolling calculations that weight recent data more heavily and may need separate reorder points for peak and off-peak periods. Many modern inventory management systems recalculate reorder points automatically using real-time sales data. Warning signs that your reorder points need adjustment include increasing stockout frequency, growing excess inventory, significant changes in lead times, or notable shifts in demand patterns after promotions, new product launches, or market changes.
How do I calculate break-even point?
Break-even point is where total revenue equals total costs. In units: BEP = Fixed Costs / (Price per Unit - Variable Cost per Unit). In revenue: BEP = Fixed Costs / Contribution Margin Ratio. For example, with 50,000 dollars in fixed costs, a 100 dollar price, and 60 dollar variable cost, BEP = 1,250 units or 125,000 dollars in revenue.
References
Reviewed by Sahil, Senior Finance & Tax Editor · Editorial policy