Inventory how-to

Why you keep running out of stock

You run out because you reorder too late or order too little, usually because you are relying on gut feel or a quick glance at stock levels instead of your actual sales rate and your supplier's lead time.

Short answer: You run out because you reorder too late or order too little, usually because you are relying on gut feel or a quick glance at stock levels instead of your actual sales rate and your supplier's lead time. Stockouts are a math problem, not bad luck.

You are not tracking your real sales rate

Most stores look at "how much is left" instead of "how fast is it selling". A SKU with 50 units left looks safe, but if it sells 10 units a day, it is gone in 5 days. You need daily sales velocity for each variant, not a total count.

You are ignoring lead time

If your supplier takes 20 days to deliver and you order when you hit zero, you have already lost 20 days of sales. The order-by date has to be calculated backwards from when stock will run out, not from when it already has.

You are treating all SKUs the same

A slow mover and a bestseller cannot use the same reorder rule. If you order everything on the same monthly schedule, the fast sellers run out early and the slow ones pile up as dead stock. Each SKU needs its own reorder point based on its own sales speed and its own supplier's lead time.

You are not accounting for demand spikes or safety stock

Even a correct average sales rate will not protect you if demand jumps for a week, or if a shipment arrives a few days late. Without safety days built into the calculation, any variation past your average turns into a stockout.

Step by step

  1. Pull daily sales per variant for the last 28 to 60 days, not just total units sold.
  2. List each supplier's real lead time, including the time they actually take to dispatch, not just the quoted shipping time.
  3. Set a safety stock buffer in days for each SKU, higher for unreliable suppliers or spiky sellers.
  4. Calculate reorder point as daily sales x (lead time + safety days) for every SKU.
  5. Compare current stock plus anything on order against that reorder point weekly, not monthly.
  6. Order before you hit the reorder point, not after stock looks low.
  7. Round order quantities up to your supplier's case pack or minimum order size so you are not short again next cycle.

Worked example

Say you sell a candle that moves 6 units a day on average, and your supplier's lead time is 14 days. Your reorder point, with a 3 day safety buffer, is 6 x (14 + 3) = 102 units. If you currently have 140 units on hand and nothing on order, you are still above the reorder point, so no action yet. Once stock drops to 102 units, you need to place an order that covers lead time plus your target cover period, say 30 days total: 6 x (14 + 30) - 140 = 124 units to order, rounded up to the nearest case pack.

How SteadyShelf helps

SteadyShelf calculates this reorder point and order-by date automatically per SKU, using your 28-day sales window and each supplier's lead time and safety days, then rounds the suggested quantity to case packs. It does not do per-location forecasts, so if you stock out at one location while another has spare stock, you still need to handle that transfer manually.

$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

What if my sales are too seasonal for a 28-day average to work?

A short window will underestimate demand right before a seasonal spike and overestimate it right after. Once you have about 13 months of sales history, SteadyShelf factors in seasonality instead of relying only on the recent 28-day window, which helps smooth this out automatically.

Should I just order more of everything to be safe?

No. Over-ordering ties up cash in slow-moving stock and can lead to markdowns later. The fix is a reorder point and quantity set per SKU based on its own sales speed and lead time, not a blanket increase across your whole catalog.

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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