Inventory glossary
What is Buffer stock?
Buffer stock is extra inventory a store keeps on hand to cover unexpected spikes in demand or delays from suppliers, beyond what normal sales would require.
For a small Shopify store, buffer stock is what stands between you and a stockout when a supplier ships late or a product suddenly sells faster than usual. Without it, one bad week or one delayed shipment can mean lost sales and unhappy customers waiting on backorder.
The trick is sizing it right. Too little buffer and you run out during busy periods. Too much and you tie up cash in stock that sits on the shelf. Most stores set buffer stock per SKU based on how unpredictable that product's sales are and how unreliable the supplier's lead time is, then review it a few times a year as sales patterns change.
Formula
Example
A candle shop sells 10 units a day on average but on its busiest days sells 18. The supplier's lead time is usually 7 days but can stretch to 10 days. Buffer stock = (18 x 10) - (10 x 7) = 180 - 70 = 110 units.
Common mistakes
- Setting the same buffer stock level for every SKU regardless of how variable its demand is.
- Never revisiting buffer levels after a product's sales pattern changes, like after it goes viral or goes out of season.
- Confusing buffer stock with safety stock and double counting both when placing orders.
Buffer stock and SteadyShelf
SteadyShelf factors buffer needs into its order-by dates and suggested order quantities so you do not have to recalculate this by hand for every SKU.
Work it out for your own products with our free tool: Safety stock calculator.
SteadyShelf is launching on the Shopify App Store. Join early access to get the install link first.
Related terms
Safety stock · Reorder point · Lead time demand · Stockout · Demand variability
FAQ
Is buffer stock the same as safety stock?
They are often used to mean the same thing. Some stores use "buffer stock" more loosely for general extra inventory, while "safety stock" refers to a specific calculated amount. In practice, treat them as the same concept unless your own system defines them separately.
How often should I update my buffer stock levels?
Check buffer stock whenever a supplier's lead time changes, at the start of a new season, or at least twice a year. Products with steady, predictable sales need less frequent review than ones with spiky or seasonal demand.
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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