Inventory how-to

How to plan inventory for a sale or promotion

Estimate the sales rate you expect during the promotion, not your normal daily rate, then order enough to cover that rate for the full promo period plus your supplier lead time.

Short answer: Estimate the sales rate you expect during the promotion, not your normal daily rate, then order enough to cover that rate for the full promo period plus your supplier lead time. Place the order early enough that stock lands before the sale starts, with a buffer for delays.

Start with a demand estimate, not your normal average

Your everyday forecast is based on recent sales history, usually a 28-day window. A promotion can push sales well above that, so you need to manually estimate a multiplier. Look at how past sales or discounts performed for the same or similar products, if you have that data. If you don't, use a conservative multiple of normal daily sales and round up rather than down, since running out mid-promotion is usually worse than holding a bit of extra stock.

Work backwards from your promotion date

Figure out your supplier's lead time and add a safety margin, then count back from the promotion start date to get your order-by date. If your lead time is long, you may need to commit to promo quantities before you have firm sales numbers, so build in a buffer for uncertainty.

Check case packs and minimums against promo quantities

Promo order quantities often don't divide evenly into standard case packs. Round up to the nearest full case rather than short yourself, and check that the rounded quantity still fits what you can realistically sell plus hold as normal stock afterward, so you are not stuck with excess inventory once the promotion ends.

Plan for the post-promotion dip

Sales usually drop below normal for a while after a promotion ends, as customers who would have bought later bought early instead. Expect your automated reorder suggestions to look too high right after a promo, since they are based on inflated recent sales. Manually adjust or wait for the sales window to normalize before trusting the regular forecast again.

Step by step

  1. List the SKUs going into the promotion and pull current on hand and on order for each.
  2. Estimate expected daily sales during the promotion based on past promo performance or a conservative multiplier of normal sales.
  3. Calculate order quantity as expected daily sales x (promo length + lead time + safety days) minus stock already on hand or on order.
  4. Round the order quantity up to the supplier's case pack and check it meets any order minimum.
  5. Count back from the promotion start date by the supplier's lead time plus safety days to get your order-by date, and place the order by then.
  6. Confirm partial or split deliveries with the supplier if the order is large, so you can receive stock as it arrives.
  7. After the promotion, expect lower than normal sales for a while and manually sense-check reorder suggestions before approving them.

Worked example

Say a store normally sells 10 units a day of a SKU, and expects the promotion to triple that to 30 units a day for a 7-day sale. Lead time is 5 days and safety stock is 2 days. Order quantity = 30 x (7 + 5 + 2) minus (40 on hand + 0 on order) = 30 x 14 - 40 = 420 - 40 = 380 units. If the case pack is 50, round up to 400 units and place the order at least 7 days before the sale starts to cover the 5-day lead time and 2-day safety buffer.

How SteadyShelf helps

SteadyShelf's forecast is built from recent sales history and won't predict a promotion spike on its own, so you need to manually override the suggested quantity for promo SKUs. It will still calculate the order-by date from your supplier's lead time and safety days, round to case packs, and draft the PO once you give it the quantity you want.

$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.

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FAQ

Will SteadyShelf automatically increase order quantities for a planned sale?

No. It forecasts from recent sales history, usually a 28-day window, and has no way to know a promotion is coming. You need to estimate the expected demand yourself and enter or adjust the order quantity manually before approving the PO.

How do I stop the reorder suggestions from overordering right after a promotion ends?

Expect suggested quantities to run high for a while, since they are based on the inflated sales from the promo period. Manually reduce or skip reorders until enough normal sales days have passed for the 28-day window to reflect typical demand again.

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.

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