Reorder Point Formula + Free Calculator (2026)

What Is a Reorder Point?#

A reorder point (ROP) is the inventory level at which you should place a new order with your supplier. When stock drops to this number, it's time to reorder — if you wait longer, you risk running out before the new shipment arrives.

Think of it like the fuel gauge in your car. You don't wait until the tank is empty to fill up. You refuel when it hits a certain level — enough to get you to the gas station without running dry. A reorder point works the same way for inventory.

The Reorder Point Formula#

```

Reorder Point = Lead Time Demand + Safety Stock

```

Where:

• Lead Time Demand = Average Daily Demand x Lead Time (in days)
• Safety Stock = buffer inventory to cover variability (see Safety Stock Formula)

That's it. The formula itself is simple. The work is in getting accurate inputs.

Worked Example: Basic Scenario#

Your situation:

• You sell 15 units per day on average
• Your supplier takes 8 days to deliver after you place an order
• You keep 30 units of safety stock

```

Lead Time Demand = 15 x 8 = 120 units

Reorder Point = 120 + 30 = 150 units

```

Action: When stock drops to 150 units, place your order. The 120 units will cover normal sales during the 8-day wait. The 30 units of safety stock protect you if sales run higher than average or the delivery comes a day or two late.

Worked Example: Seasonal Product#

Your situation: You sell outdoor furniture. Average daily sales vary by season:

*Lead time increases in summer because the supplier is also busier.

Notice how dramatically the reorder point changes — from 40 units in winter to 330 in summer. If you use a single reorder point year-round, you'll either stock out in summer or waste money warehousing excess in winter.

Key takeaway: Review and adjust reorder points at least seasonally. Monthly is better for items with significant demand variation.

Worked Example: Multiple Suppliers#

Your situation: You source the same widget from two suppliers:

You sell 10 units per day with 15 units of safety stock.

Reorder point for Supplier A:

```

ROP = (10 x 5) + 15 = 65 units

```

Reorder point for Supplier B:

```

ROP = (10 x 30) + 60 = 360 units

```

Note the much larger safety stock for Supplier B — overseas shipping has more variability, so the buffer needs to be bigger.

Practical strategy: Use Supplier B for regular replenishment (cheaper) and Supplier A as a fast backup when Supplier B is late or demand spikes unexpectedly. Set your primary reorder point at 360 (trigger Supplier B order), and a secondary alert at 65 (trigger emergency Supplier A order if Supplier B hasn't arrived).

Getting Accurate Inputs#

The formula is only as good as its inputs. Here's how to get them right.

Average Daily Demand

Don't guess. Pull actual sales data from the last 3-6 months (or a full year if your product is seasonal).

```

Average Daily Demand = Total Units Sold in Period / Number of Days in Period

```

Example: You sold 1,800 units over the past 90 days.

```

Average Daily Demand = 1,800 / 90 = 20 units per day

```

Watch out for:

• Including promotional periods that inflated demand (if the promotion isn't recurring)
• Periods where you were stocked out (zero sales doesn't mean zero demand — you just couldn't fulfill it)
• New products without enough history (use conservative estimates and adjust as data comes in)

Lead Time

Lead time is the total time from placing an order to having the stock available to sell. This includes:

1. Order processing time — how long before the supplier starts working on your order (often 1-2 days)
2. Production time — if made to order
3. Transit time — shipping from supplier to your location
4. Receiving time — how long it takes you to receive, inspect, and put away the shipment (often overlooked — typically 0.5-2 days)

Example:

• Order processing: 1 day
• Supplier ships from stock: 0 days production
• Ground freight: 5 days
• Your receiving process: 1 day
• Total lead time: 7 days

Many businesses only count the transit time and forget about processing and receiving. This leads to reorder points that are 2-3 days too low.

Track actual lead times, not quoted lead times. Record when you place each order and when you receive it. After 5-10 orders, you'll have a reliable average — and you'll know the variance, which feeds into your safety stock calculation.

Safety Stock

See the full guide: How to Calculate Safety Stock.

Quick version for those just starting out:

```

Safety Stock = (Max Daily Sales x Max Lead Time) - (Avg Daily Sales x Avg Lead Time)

```

Example:

• Max daily sales: 30 units
• Max lead time: 10 days
• Avg daily sales: 20 units
• Avg lead time: 7 days

```

Safety Stock = (30 x 10) - (20 x 7) = 300 - 140 = 160 units

```

If this seems like a lot of buffer, it is — the simple formula is conservative. As you build up data, switching to the statistical formula (Z x oLT) usually results in lower, more efficient safety stock levels.

Handling Variable Demand#

Real demand isn't a straight line. Here's how to handle common patterns.

Growing Demand

If your average daily sales are increasing month over month, using a 6-month average will underestimate current demand. Use a weighted average that gives more importance to recent months:

Example:

A simple average is 18.3. But the trend is clearly upward. Use the most recent full month (22) or a 2-month weighted average ((18 + 22) / 2 = 20) for your reorder point calculation.

Declining Demand

The reverse applies. If a product is winding down, don't use a 6-month average that includes the higher earlier months. Reduce your reorder point to avoid being stuck with excess stock.

Promotional Spikes

If you're planning a promotion that will temporarily increase demand, manually adjust your reorder point in advance. After the promotion, revert.

Example: Normal reorder point is 150. You're running a 20%-off sale that you expect will double daily sales for two weeks. Temporarily increase the reorder point to 270 (accounting for higher demand during the lead time period).

Multiple Locations#

If you stock the same item at multiple locations, calculate a separate reorder point for each one. Don't use aggregate demand. This is especially important for warehouses and retail stores operating across multiple sites.

Why: A central warehouse selling 100 units/day and a satellite location selling 5 units/day have very different replenishment needs. A combined reorder point would over-stock the satellite and under-stock the warehouse.

Transfer consideration: If you can transfer between locations in 1-2 days, the satellite location might use a lower safety stock — it can pull from the central warehouse in a pinch. Factor transfer lead time into the satellite's formula.

Automating Reorder Points#

Manually monitoring stock levels against reorder points works when you have 20-30 SKUs. At 100+, it's impractical.

Inventory software can:

• Alert you when stock drops to the reorder point (email, SMS, dashboard notification)
• Auto-calculate reorder points based on your historical sales velocity and supplier lead times
• Adjust dynamically as demand patterns shift — no quarterly spreadsheet exercise needed
• Generate purchase orders automatically when the reorder point is hit (for businesses that want full automation)

The value isn't just in avoiding stockouts. It's in freeing up your time. Instead of checking stock levels every morning, you respond to alerts and focus on running the business.

Common Mistakes#

Setting Reorder Points Too Low

This usually happens when businesses exclude safety stock ("we'll just order when we get low") or undercount lead time. The result: chronic stockouts on popular items.

Never Updating Reorder Points

A reorder point calculated in January using January data will be wrong by June if demand has shifted. At minimum, update quarterly. Update immediately when:

• You change suppliers (different lead time)
• Demand trends shift significantly
• You're entering or exiting your peak season

Reorder Point at Zero

Some businesses don't set reorder points at all and just order when they run out. This guarantees a stockout lasting the full lead time on every replenishment cycle. Even a rough reorder point is better than none.

Ignoring Minimum Order Quantities

Your formula might say to reorder when you hit 100 units and order 200 units. But if the supplier minimum is 500 units, you need to factor that in — you'll be ordering less frequently but in larger quantities, which changes the dynamics.

The reorder point formula is foundational. Get it right for your top 20 items and you'll eliminate most of your stockout pain. Extend it to all items and you'll have a disciplined, data-driven replenishment process.

Try it now: Use our free reorder point calculator → — enter your daily demand, lead time, and safety stock to get your reorder trigger in seconds. No signup required.

Related: Free reorder point calculator | Free safety stock calculator | Safety stock formula | Inventory management software with demand forecasting | Inventory best practices

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