Free Reorder Point Calculator

What Is a Reorder Point Calculator?

A reorder point calculator tells you the exact inventory level at which you should place a new purchase order. Instead of guessing when to restock — or waiting until you're already out of stock — you enter your sales data and supplier lead times, and the calculator gives you a precise number. When your stock drops to that level, it's time to order. This tool automatically calculates your safety stock and adds it to your demand during lead time, giving you a reorder point that accounts for both normal consumption and unexpected variability.

How Does the Reorder Point Formula Work?

The reorder point formula has two components:

Reorder Point = (Average Daily Sales × Average Lead Time) + Safety Stock

The first part — average daily sales × average lead time — calculates how many units you'll sell while waiting for your supplier to deliver. If you sell 30 units per day and your supplier takes 7 days, you'll need 210 units to cover that window. The second part — safety stock — adds a buffer to protect against higher-than-usual demand or late deliveries. This calculator uses the Z-score method to compute safety stock automatically based on your variability data and target service level. For a deeper explanation of lead time and its impact on inventory, see our lead time calculator.

Why Is the Reorder Point Important for Ecommerce?

For sellers operating across multiple marketplaces — Shopee, Lazada, Amazon, TikTok Shop, Shopify — the reorder point prevents two costly problems. Ordering too late means stockouts, lost sales, and marketplace ranking penalties (Shopee and Lazada both penalise sellers who cancel orders due to stock issues). Ordering too early ties up cash in excess inventory and increases warehousing costs. The reorder point is the sweet spot: order exactly when you need to, not a day before or after. If you manage inventory across platforms, tools like OneCart can centralise your stock levels so you always know exactly where you stand.

Reorder Point vs Safety Stock vs EOQ

These three inventory formulas work together but answer different questions. Safety stock answers "how much buffer do I need?" — it's the extra units held to prevent stockouts. The reorder point answers "when should I order?" — it's the trigger level that tells you to place a purchase order. Economic order quantity (EOQ) answers "how much should I order?" — it's the optimal order size that minimises combined ordering and holding costs. Use our EOQ calculator to determine the right quantity, then use this reorder point calculator to determine the right timing. Together, they form a complete replenishment strategy.

How to Set Up Reorder Point Alerts

Calculating your reorder point is step one — the real value comes from monitoring your stock levels against it. Most inventory management software lets you set low-stock alerts at your reorder point. When stock drops to that level, you get notified automatically. For multichannel sellers, this is critical because sales happen simultaneously across platforms. A product might look fine on one marketplace while being dangerously low when you add up orders from Shopee, Lazada, and your Shopify store. Learn more about how safety stock fits into your overall strategy in our safety stock guide.

Common Reorder Point Mistakes

The most common mistake is using a single reorder point across all products. Your bestsellers and slow-movers have completely different demand patterns and need different reorder points. Use ABC analysis: calculate precise reorder points with 95% service levels for A-items (top 20% by revenue), and simpler calculations with 90% service levels for B and C items. The second mistake is never updating — demand patterns shift seasonally, suppliers change lead times, and what worked six months ago may no longer be accurate. Recalculate quarterly, or monthly for seasonal products.