The reorder point formula is one of the simplest tools in inventory management, and one of the most profitable when you use it well. It tells you the exact stock level at which to place your next purchase order: early enough to avoid running out, but not so early that you tie up cash in shelves of product you don't need yet.
For online brands, reorder timing is everything. U.S. e-commerce hit $316.1 billion in the fourth quarter of 2025 (about 16.6% of all retail sales), and that share has climbed steadily for years.
In a market that is competitive, every stockout is a sale handed to someone else. Get your reorder points right, and you keep your best-sellers available, your customers loyal, and your revenue moving in the right direction.
A reorder point (ROP) is the lowest stock level a product should hit before you reorder it. When inventory drops to that number, it's your cue to send a purchase order to your supplier. Soon enough, the new shipment will arrive before you sell out. You'll sometimes see it called the reorder level, or ROL; the terms are interchangeable.
An ROP isn't a single fixed number you set once and forget. It's specific to each product (or SKU) and shifts as your sales velocity, suppliers, and seasons change. A fast-moving lip balm with a two-week supplier lead time will land at a very different level than a niche supplement you restock once a quarter.
💡 Tip: Calculate reorder points per SKU, not across your whole catalog. A blanket number that "feels about right" almost always leaves your top sellers exposed and your slow movers overstocked.
Here's the calculation in its most usable form:
➡️ Reorder point = (average daily sales × lead time in days) + safety stock
That single line captures three realities of running a product business: how quickly an item leaves your shelves, how long it takes to replace, and how much of a buffer you want against the unexpected. The first two multiplied together are your lead time demand; the units you expect to sell while you wait for a restock. Add safety stock, and you've got the trigger that keeps you covered. This is the same logic baked into nearly every modern warehouse management system.
Knowing how to calculate the reorder point comes down to nailing three inputs. Let's break each one down, then run a full example.
Divide the total units sold over a period by the number of days in that period. If you sold 1,200 units of a face serum over the last 30 days, your average daily sales are 40 units. Pull at least three to six months of data where you can. The longer the window, the more your numbers smooth out seasonal noise.
Lead time is the number of days between placing a purchase order and having that stock ready to sell. Track it from your past orders and take an average. If you're working with a new supplier or shipping across borders, build in a little extra cushion until their reliability is proven. Reorder points matter most when supplier timelines are hard to predict, and stockouts are expensive.
Safety stock is the buffer you hold for the "just in case", like a demand spike, a delayed shipment, or a product lost in transit. A common way to size it:
Safety stock = (max daily sales × max lead time) − (avg daily sales × avg lead time)
It's worth getting this number right, because it's the piece most brands either skip or guess at.
Say you run a skincare brand and want to set the reorder point for your hero serum:
|
Input |
Value |
|---|---|
|
Average daily sales |
40 units |
|
Average lead time |
7 days |
|
Maximum daily sales |
60 units |
|
Maximum lead time |
12 days |
|
Reorder Point (Result) |
720 units |
Here's the reorder point calculation step by step:
So when your serum inventory drops to 720 units, you place your next order. Even if demand surges to its peak and your supplier takes their longest, you should still have product on the shelf when the restock lands.
💡 Tip: Set reorder points per location, too. If you store inventory in more than one warehouse, each one needs its own number based on the demand and lead time it actually sees.
The safety stock vs reorder point comparison confuses a lot of people, because the two are tightly linked but play different roles. The simplest way to keep them straight:
|
Safety Stock |
Reorder Point |
|
|---|---|---|
|
What It Is |
Extra buffer inventory |
A stock-level trigger |
|
Its Job |
Absorbs surprises |
Tells you when to reorder |
|
Relationship |
A component of the trigger |
Includes safety stock in its math |
In short, safety stock is your backup layer, while the reorder point is the trigger that tells you to restock before that backup gets touched.
Once you know when to reorder, the natural next question is how much to order. That's where Economic Order Quantity comes in.
EOQ (Economic Order Quantity) is the order size that minimizes your combined ordering and holding costs. First developed by Ford W. Harris back in 1913, it's one of the oldest models in inventory management and is still widely used. The formula is:
➡️ EOQ = √(2DS ÷ H)
Where:
The result is your sweet spot: order in batches that big, and you're not overpaying in shipping and handling from ordering too often, nor bleeding cash on carrying costs from ordering too much.
No. They answer two different questions and shouldn't be confused. The reorder level (ROL, another name for the reorder point) tells you when to place an order. EOQ tells you how much to order once you do. Use them as a pair: your trigger fires the signal, and your EOQ sizes the response.
You don't need fancy software to start. A spreadsheet works fine for a manageable catalog. In Excel or Google Sheets, dedicate columns to average daily sales, lead time, and safety stock, then build a reorder-point column with a simple formula such as =(B2*C2)+D2. Add conditional formatting so a cell turns red the moment on-hand quantity falls to or below that number, and you've got a free, visual low-stock alert.
The catch is upkeep. Spreadsheets don't update themselves, and as your SKU count and order volume climb, manual recalculation becomes a real risk to your accuracy. That's the point where most growing brands move their triggers into an ecommerce inventory management platform, where live sales data and automated alerts do the watching for you.
The Fulfillment Lab pairs real-time inventory visibility with hands-on e-commerce fulfillment services.
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It's easy to think of reorder points as defensive housekeeping. In reality, they're a growth lever. Here's how a well-tuned trigger directly protects and grows revenue:
That last point is where fulfillment strategy meets the math. A perfect reorder point still depends on inventory being positioned close to your customers and moving the moment an order comes in. That's the difference between a number on a spreadsheet and a shipment on a doorstep.
A reorder point is only as good as the operation behind it. The Fulfillment Lab pairs real-time inventory visibility with hands-on ecommerce fulfillment services. Once your stock hits its trigger, replenishment, pick and pack, kitting, and fast nationwide shipping all keep moving without you “babysitting a spreadsheet”.
If you're ready to stop guessing at stock levels and start keeping your best-sellers available, we'd love to show you how it works.
In a spreadsheet, the reorder point formula is =(average daily sales × lead time) + safety stock, for example, =(B2*C2)+D2. Add conditional formatting to flag cells in red when on-hand stock drops to that level.
No. ROL (reorder level, also called the reorder point) tells you when to place an order, based on demand and lead time. EOQ tells you how much to order to minimize total inventory costs. They're complementary, not interchangeable.
A pet-supplies brand sells 25 units of a chew toy daily, with a 10-day lead time and 100 units of safety stock. Its reorder point is (25 × 10) + 100 = 350 units. They’ll need to reorder when stock hits 350.
Review your triggers at least quarterly, and any time you switch suppliers, see lead times shift, or hit a seasonal swing. Reorder points drift as demand and supply change, so stale numbers quietly reintroduce stockout and overstocking risks.
It's the pairing of two models: the reorder point signals when to order, and EOQ determines the ideal order size at that moment. Used together, they minimize ordering and holding costs while protecting against stockouts.