How to Plan Inventory for Black Friday & Cyber Monday: A Shopify Merchant’s Guide

Most Shopify merchants plan BFCM inventory the same way. They open last year’s numbers, pick a growth percentage that feels about right, and place an order. Then a bestseller sells out on day 2, or a few products are still sitting in the stockroom in February.

Last year’s sales numbers can mislead you. They show what you sold, not what you could have sold if you hadn’t run out. This guide covers how to fix that, how much to order, and the date your purchase order has to go out.

If you’d rather not do the math by hand, IFH’s Sam AI BFCM Planner does all of it inside the app. Keep reading if you want to see how the numbers work, or if you only have a few products to plan.

Step 1: Start With Last Year’s BFCM Sales, and Correct Them

Pull last year’s BFCM sales for every product you plan to stock. Use them as a starting point, not the final number.

If a product ran out of stock during BFCM, its sales figure is too low. Sales stopped because the stock ran out, not because people stopped wanting it. You need to estimate what it would have sold if the shelf had stayed full.

Worked example

• Last year’s BFCM window: 8 days
• The product sold out on day 3
• Units sold in those 3 days: 30

Daily rate while it was in stock: 30 ÷ 3 = 10 units per day.

Corrected demand for the full 8 days: 10 × 8 = 80 units.

So your real baseline is 80 units, even though your sales report says 30.

To find the day a product ran out, check the inventory history on the product page in Shopify and look for when the available quantity hit zero. A rough date is fine. “Around day 3” gets you much closer than ignoring the stockout completely.

Step 2: Apply Your Growth Assumption

Now take the corrected baseline and apply the growth you expect this year. This one is your call, since you know the business better than any tool does. Things to think about:

• How much has your store grown this year compared to last year?
• Are you running a bigger promotion than last BFCM?
• Is this product new, picking up speed, or fading?
• Have you added new marketing channels?

Worked example

• Corrected demand last BFCM: 80 units
• Expected growth: 20%
• Expected demand this year: 80 × 1.20 = 96 units

Round it to 100 units to keep the ordering simple.

Set growth per product, or at least per category. A bestseller you’ve sold for three years and a product you launched in October last year will not grow at the same rate. Also ask what happens if you only hit half of your growth number. You want enough stock to cover a good year without being stuck with the leftovers after a bad one.

Step 3: Work Out What You’ll Have on Hand When BFCM Starts

Your demand number tells you how much you need to sell. How much you need to order depends on what you’ll have in stock when BFCM begins, and that is different from what you have today.

Between now and BFCM you’ll keep selling at your normal rate, and any inventory already on order will arrive. So:

Available at BFCM start = current stock − units sold before BFCM + incoming inventory arriving before BFCM

Worked example

• Current inventory: 60 units
• Days until BFCM: 52
• Normal daily sales: 0.8 units
• Sold before BFCM: 52 × 0.8 = 41.6, so about 42 units
• Already on order and arriving before BFCM: 20 units

Available at BFCM start: 60 − 42 + 20 = 38 units.

You expect to sell 100, and you’ll have 38. You need to order 62 units, not 100. This is the gap order. Ordering your full forecast ignores the stock you already have and the stock already on its way, and that’s how stores end up overstocked.

Only count incoming inventory that will actually arrive before BFCM. A shipment landing on November 25 does you no good for a November 21 start. If your incoming stock is tracked with Shopify’s new PO and Transfer workflow, the arrival date is on the linked Transfer. We explain that in Shopify Changed How Purchase Orders Work.

Step 4: Add Safety Stock

Your demand number is a guess. Suppliers ship late sometimes, and BFCM can go better than you planned. Safety stock is the extra you order to cover that.

How much depends on how sure you are about demand and how much you trust your supplier. A rough guide, as a percentage of your gap order:

• 10-15%: reliable supplier, product with a steady sales history
• 20-25%: some uncertainty about demand or delivery
• 30% or more: new product, unreliable supplier, or a very high growth assumption

Worked example

• Gap order: 62 units
• Safety stock at 20%: 62 × 0.20 = 12.4, so 13 units
• Final order: 62 + 13 = 75 units

Then multiply the order quantity by your unit cost and compare it with your BFCM inventory budget. If you’re planning many products and the total goes over budget, cut the safety stock on your low-margin products first and protect the buffer on your best sellers.

Step 5: Find Your Purchase Order Deadline

Get this one right or nothing else matters. A perfect plan is useless if the order goes out too late.

PO deadline = BFCM start date − supplier lead time − buffer days

Buffer days cover shipping delays and customs holds. Use 3 to 5 days for a domestic supplier and more for anything shipped from overseas.

Worked example

• BFCM start date: November 21, 2026
• Supplier lead time: 30 days
• Buffer: 5 days

November 21 minus 35 days is October 17, 2026.

If you’re reading this at the end of September with a 30-day lead time, you have about two weeks. If your lead time is 45 to 60 days, the deadline may have already passed, and you should call your supplier today to ask what they can still deliver in time.

Do this calculation first, before anything else in this guide. It tells you how much time you have left for the rest.

Step 6: Check the Plan Before You Send the Order

Take a few minutes to check the numbers before the PO goes out.

Compare your expected BFCM demand with your normal month. If it comes out at more than 4 or 5 times a regular month of sales, look at it again. That can be right for a store that’s growing fast, but you should be able to explain why.

Ask your supplier whether they can fill the order in your lead time. If you’re ordering a lot more than usual, a 30-day lead time can turn into 45.

Think about what happens if the shipment shows up late. If it’s due on November 20 and BFCM starts on November 21, a two-day delay leaves you with empty shelves. For your top products, see if a smaller backup order from a closer supplier makes sense.

Planning Across Your Whole Catalog

Doing this for 5 products is fine. Doing it for 50 means pulling stockout dates for each one, choosing a growth rate for each one, working out the gap, and keeping track of different lead times from different suppliers.

IFH: Inventory Forecasting Hero does this automatically with its AI BFCM Planner, Sam. It pulls last year’s BFCM data from your Shopify store, corrects for stockout days, applies your growth assumptions, subtracts what you’ll sell before BFCM, adds the inventory already in transit, and builds in safety stock based on how reliable your supplier is. You get a buy plan with a PO deadline for every product you pick, plus an explanation of how it got each number. The full walkthrough is in Meet Sam, IFH’s BFCM Planner.

Sam follows the same steps as this guide, using data your store already has.

Common BFCM Inventory Mistakes

• Using raw sales numbers. If your top products sold out early last year, your demand data is too low across the board. Check for stockouts before you set growth.
• Ordering the full forecast. What you need to buy is the gap, not the total demand.
• Forgetting incoming inventory. Stock already on order counts toward what you’ll have at peak. Ordering on top of it leaves you overstocked.
• Using one growth rate for every product. Different products are at different stages, so they grow differently.
• Placing the PO late. If your supplier needs 45 days and it’s already mid-October, you’re behind.

FAQ

When should I start BFCM inventory planning? Now. If your supplier lead time is 30 to 60 days, purchase orders need to go out by early to mid-October to arrive before BFCM. Count back from your BFCM start date using your lead time, and that gives you your deadline.

How do I correct for stockout days if I don’t know exactly when a product ran out? Look at the inventory history in Shopify to find roughly when the available quantity hit zero. A rough date such as “around day 3” is enough. You’re estimating what demand would have been with stock on the shelf, so it doesn’t have to be exact to the day.

What growth percentage should I use for BFCM? Pick it per product. Think about how much your store has grown this year, how that product has been trending, and whether your promotions or marketing are changing. One percentage for everything will be too high for some products and too low for others.

How much safety stock do I need for BFCM? A good starting point is 15 to 25 percent of your gap order. Go higher for a new product with no BFCM history or a supplier who’s sometimes late.

What is a gap order? It’s the difference between the stock you need for BFCM and the stock you’ll have when BFCM starts. The stock you’ll have includes what’s left after normal sales between now and then, plus anything already on order that arrives in time.

Does IFH: Inventory Forecasting Hero help with BFCM planning? Yes. IFH: Inventory Forecasting Hero has an AI BFCM Planner called Sam that does every step in this guide for each product you select. Read more here: Meet Sam.