Inventory how-to

How to forecast inventory for Black Friday and Cyber Monday

Forecast Black Friday and Cyber Monday (BFCM) by looking at last year's actual sales for the same days, not your normal 28-day average.

Short answer: Forecast Black Friday and Cyber Monday (BFCM) by looking at last year's actual sales for the same days, not your normal 28-day average. If you do not have last year's data, build a manual multiplier from your best guess of demand lift and apply it on top of your usual daily sales rate, then order early because supplier lead times do not shrink just because it is November.

Why normal forecasting breaks down for BFCM

A rolling 28-day sales window is built for steady demand. BFCM is a spike, often several times your normal daily rate for just a few days. If you order based on recent average sales, you will run out early on your best day of the year.

Use last year's BFCM data if you have it

Pull the actual units sold per variant for last year's Black Friday and Cyber Monday. Compare that to the average daily sales in the weeks before it, to get a rough multiplier per product. Apply that multiplier to this year's current daily sales rate as a starting point, then adjust for any known changes like new products, discontinued lines, or a bigger marketing push.

Build a manual estimate if you have no history

If this is your first BFCM, or the product is new, estimate a multiplier from your own judgment: how big a discount you are running, how much traffic you expect, and how similar products performed on past promo days. Apply it manually to your daily sales rate and treat the result as a planning number, not a guarantee. Round up on fast movers and key SKUs, since running out costs more than carrying a bit extra for a few weeks.

Order early and build in a buffer

Add your BFCM demand bump as extra days of cover on top of normal safety stock, and place the order well before your supplier's lead time would normally require it. Suppliers get busy in Q4 too, so lead times can stretch. If a SKU normally needs ordering 14 days out, treat BFCM stock as needing 21 to 30 days out to leave room for delays.

Step by step

  1. Export last year's unit sales per variant for Nov 24 to Nov 27 (or your BFCM dates)
  2. Calculate the multiplier: BFCM daily rate divided by normal daily rate, per SKU
  3. Apply that multiplier to this year's current daily sales rate for each variant
  4. For new products, estimate a multiplier manually based on discount depth and expected traffic
  5. Add the extra BFCM units as additional days of cover in your reorder point calculation
  6. Place supplier orders earlier than usual to account for Q4 lead time delays
  7. Recheck stock levels in the week before BFCM and top up any SKU trending ahead of plan

Worked example

Last year, a candle brand sold 8 units a day of its bestseller normally, but sold 320 units total across the 4-day BFCM weekend, or 80 units a day, a 10x multiplier. This year the normal daily rate has grown to 12 units a day, so the store applies the same 10x multiplier to forecast 120 units a day over BFCM, or 480 units for the weekend. With 15 days of lead time plus a 10-day Q4 delay buffer and 5 days of safety stock, the reorder point becomes 12 x (15+10+5) = 360 units, and the store orders enough to also cover the 480-unit BFCM spike on top of that.

How SteadyShelf helps

SteadyShelf's default forecast uses a 28-day sales window and only picks up seasonality once it has about 13 months of history, so it will not automatically spot a BFCM spike on its own in year one. Once you have a full year of data, its seasonality adjustment can factor in last year's BFCM bump, but for now you should manually pad your order-by quantities for key SKUs before the event using the multiplier approach above.

$29/month flat, unlimited products and suppliers, 30-day free trial. Run the numbers now with the free reorder point calculator.

SteadyShelf is launching on the Shopify App Store. Join early access to get the install link first.

Related guides

All inventory how-to guides ยท Inventory glossary

FAQ

Will SteadyShelf automatically increase my reorder quantities before Black Friday?

Only once it has roughly 13 months of sales history to learn the seasonal pattern. Before that, its forecast is based on your recent 28-day average and will not anticipate a one-off spike, so you need to manually adjust order quantities for BFCM yourself.

Should I order extra stock for every SKU or just bestsellers?

Focus on the SKUs that actually drove BFCM sales last year, usually a small number of bestsellers and promo items. Padding every SKU equally ties up cash and risks overstock on slow movers that will not see a BFCM bump at all.

Let SteadyShelf do this math for every SKU

Order-by dates per supplier, seasonal forecasts and draft POs for your Shopify store. $29/month after a 30-day free trial.

Get early access