How Do I Know How Much Inventory to Reorder? A Practical Guide for SMBs

‍Key Takeaways

• Reorder quantity decisions require context, not guesswork. Accurate replenishment depends on sales history, open orders, inbound stock, and current inventory—not just quantity on hand.
• Automatic replenishment replaces manual calculations with data-driven logic. HandiFox calculates reorder quantities using real sales data and commitments, reducing overstocking, stockouts, and rushed purchasing decisions.
• Different business models require different replenishment methods. Whether you restock on a schedule, plan to a future date, manage by thresholds, or want early risk alerts, HandiFox offers a method tailored to each approach.
• Forecasting visibility helps prioritize what to reorder first. Quantity on Hand Forecasting shows how long inventory will last, helping teams identify risk early before stock levels become critical.
• Vendor constraints are built into the math. Case sizes and rounding rules are applied automatically, ensuring reorder quantities align with how suppliers actually sell, no manual adjustments needed.

Knowing when to reorder is only half the challenge. The harder question, and the one most small businesses struggle with,  is how much to reorder without overstocking, tying up cash, or running out too soon.

Many teams rely on gut feeling, spreadsheets, or simple reorder points. That approach works until sales fluctuate, open orders pile up, or vendor lead times change. At that point, manual calculations become unreliable and time-consuming.

HandiFox solves this problem with Automatic Replenishment, a set of replenishment methods that calculate reorder quantities based on real sales data, open orders, and current stock levels. Instead of guessing, you choose the logic that matches how your business operates and let the system do the math.

This article explains how to decide which replenishment method to use and how each one answers the question: “How much should I reorder right now?”

Why “Quantity to Reorder” Is Harder Than It Sounds

Most reorder mistakes come from ignoring context. Quantity on hand alone is not enough.

To reorder accurately, you need to account for:

• what you’ve already sold
• what customers have ordered but not received
• what suppliers are already shipping to you
• how fast items typically move

When these factors are handled manually, it’s easy to double-order, under-order, or react too late. Automatic replenishment exists to remove that uncertainty.

Automatic Replenishment in HandiFox: The Big Picture

HandiFox’s Automatic Replenishment feature allows you to generate purchase orders based on actual demand, not assumptions. From the Automatic Replenishment screen, you select the site you want to replenish and choose the calculation method that fits your workflow.

The key is understanding which replenishment logic matches your business model. HandiFox offers four options, each answering the reorder-quantity question in a different way.

In addition to the calculations themselves, the replenishment screen provides helpful controls, including the ability to:

• view all items or only those that need reordering
• see preferred and alternative vendors for each item
• include or exclude quantities on open sales and purchase orders

Once these options are set, you can either review data-driven suggestions or let the system generate replenishment purchase orders automatically.

Reorder Based on Quantity Sold for a Period

Best for: Regular, predictable restocking cycles

This method works well if you reorder on a fixed schedule (weekly, bi-weekly, or monthly) and want to replenish what you expect to sell before the next reorder.

Instead of asking “How many do I have?”, this method asks: “How many did I sell, and how many do I need to cover what’s already committed?”

The system:

• calculates how many units were sold since a chosen date
• adds quantities on open sales orders
• subtracts quantities already on open purchase orders
• subtracts what you currently have on hand

Formula 

Reorder Quantity = Quantity Sold (since selected date) + Quantity on Open Sales Orders − Quantity on Open Purchase Orders − Current Quantity on Hand

Real-Life Example

• Starting inventory on Monday: 10 pens
• Sold during the week: 7 pens
• Open sales orders: 5 pens
• Open purchase orders: 4 pens
• Current QOH: 3 pens

Reorder quantity: (7 + 5) - 3 - 4 = 5

In practical terms, you need 12 pens to cover expected demand. Since 3 are already on hand and 4 are inbound, ordering 5 more closes the gap. This method is especially useful for consumables, fast-moving SKUs, and businesses that restock on a regular cadence.

In HandiFox Online, you can review the calculated quantities, select vendors, choose which items to include, and generate purchase orders with a single click.

Reorder Based on Average Sales Rate

Best for: Planning stock to last until a future date

If your question is “How much do I need to last until next month?”, this method gives a clearer answer.

Instead of looking at total sales, HandiFox calculates your average daily sales rate for a product over a selected period. It then projects how much inventory you’ll need between now and a target date in the future.

From there, the system:

• adds open sales orders
• subtracts open purchase orders
• subtracts current quantity on hand

The resulting number reflects how much you need to order to stay stocked through the selected period.

Formulas

Average Daily Sales = Total Units Sold ÷ Number of Days

Required Quantity = (Average Daily Sales × Days Until Target Date) + Open Sales Orders − Open Purchase Orders − Current QOH

Real-Life Example

• Units sold in last 30 days: 54 pens
• Average daily sales: 1.8 pens/day
• Planning horizon: 14 days
• Open sales orders: 5 pens
• Open purchase orders: 4 pens
• Current QOH: 3 pens

Average daily sales: 1.8 × 14 = 25.2

Quantity to reorder: 25.2 + 5 − 4 − 3 = 23.2

HandiFox will round based on your case size and rounding rules.

This method is ideal for businesses with steady demand patterns or those planning ahead for known cycles, promotions, or seasonal changes.

Reorder Using Reorder Point and Desired Quantity on Hand

Best for: Threshold-based, control-oriented inventory planning

This is the most familiar replenishment model for many SMBs, but HandiFox makes it far more reliable by factoring in open orders automatically.

With this method, each product has:

• a Reorder Point (ROP) — the trigger
• a Desired Quantity on Hand — the target level

HandiFox first determines whether the product should be reordered at all by evaluating:

• current quantity on hand
• quantities on open purchase orders
• quantities on open sales orders

If stock falls at or below the reorder point, the system calculates how much to order to reach the desired level,  accounting for everything already inbound or committed.

Formula

Reorder Quantity = Desired QOH − Current QOH − Open Purchase Orders + Open Sales Orders

Real-Life Example

• Reorder Point (ROP): 3
• Desired QOH: 20
• Current QOH: 5
• Open sales orders: 7
• Open purchase orders: 4

Trigger check: 5 + 4 − 7 = 2 → below ROP → reorder triggered

Quantity to reorder: 20 − 5 − 4 + 7 = 18 

This method is ideal for businesses that want clear guardrails and predictable stock levels without constant monitoring.

Quantity on Hand Forecasting (Risk Visibility)

Best for: Understanding how long current stock will last

Sometimes the question isn’t “How much should I order?”, it’s “How close am I to running out?”

Quantity on Hand Forecasting answers that by estimating how many weeks your current inventory will last based on average weekly sales. Items only appear for replenishment if they are already at or below their reorder point. This method will not trigger the generation of a replenishment PO, it’s just there to inform you about the upcoming need to restock.

The forecast is delivered based on the average sales rate for the last 7/ 30/ 365 days.

Formula

Weeks of Inventory Left = Current QOH ÷ Average Weekly Sales

Real-Life Example

• Sold last 30 days: 54 pens
• Average weekly sales: ~12.6 pens
• Current QOH: 3 pens
• Reorder Point: 5 pens

3 ÷ 12.6 ≈ 0.24 weeks (rounded down to 0). This signals immediate risk and helps teams prioritize what to reorder first

This method is especially helpful for identifying risk early and prioritizing which products need attention first, even before quantities drop dangerously low.

Handling Case Sizes and Vendor Constraints Automatically

Reorder calculations don’t stop at demand. In real life, vendors impose constraints.

HandiFox allows you to define:

• case sizes (in case your supplier ships only in cases)
• rounding rules (round up, down, or to nearest)

These rules apply across all replenishment methods, ensuring that calculated reorder quantities align with how suppliers actually sell products. This prevents under-ordering, rejected POs, or awkward manual adjustments.

Setting Up Reorder Triggers in Bulk in HandiFox Online

Once replenishment logic is defined, consistency becomes critical. HandiFox lets you configure reorder triggers in bulk across items and sites.

To do this:

1. Go to Inventory → QOH Viewer
2. Click Reordering in the top-right corner
3. Select the Site you’re configuring
4. Enter values directly into the grid:
   
   • Reorder Point – minimum stock level before replenishment
   • Desired QOH – target stock level after replenishment
   • Case Size – vendor order multiple (if applicable)
   • Reorder Rounding – rounding logic
     
5. Click Save

From that point on, any item below its reorder point is automatically included in replenishment calculations.

Practical Tip for SMBs

A common starting strategy is:

• Set ROP = 1–2 weeks of average sales
• Set Desired QOH = 3–4 weeks of average sales

You can refine these numbers later once you see how replenishment behaves in practice.

So… How Do You Know How Much to Reorder?

The short answer is: you don’t guess, you choose the logic that matches your business and let the system calculate it for you.

• If you reorder on a schedule → use Quantity Sold for a Period
• If you plan ahead to a date → use Average Sales Rate
• If you manage by thresholds → use Reorder Point & Desired QOH
• If you want early warnings → use QOH Forecasting

All four methods rely on the same foundation: real sales data, real commitments, and real inventory levels.

Conclusion: Reordering with Confidence Instead of Guesswork

The question “How much should I reorder?” doesn’t have one universal answer. It has the right answer for your business model.

HandiFox’s Automatic Replenishment gives SMBs multiple ways to calculate reorder quantities, each grounded in real data and designed to prevent stockouts, overstocking, and rushed decisions. Whether you restock weekly, plan months ahead, or manage by thresholds, the system ensures that purchase orders reflect actual demand.

New to automated inventory control? Request a live demo of HandiFox Online.