Inventory how-to

How many days of stock should you keep

There is no single right number.

Short answer: There is no single right number. It depends on your supplier's lead time, how much the item's sales bounce around, and how much it would cost you to run out versus the cost of holding extra stock. As a starting point, keep enough stock to cover lead time plus a safety buffer, then adjust per SKU based on how it actually sells.

Start with lead time, not a guess

Your days of stock target should be built from real numbers, not a round figure like "30 days" applied to everything. The two inputs that matter most are your supplier's lead time (how long from order to delivery) and safety days (a buffer for late shipments or sales spikes). Add those together and you get your reorder point in days of stock.

Different SKUs need different targets

A fast-selling item with a long lead time needs more days of cover than a slow seller with a quick lead time. If you use one blanket number across your whole catalog, you will end up overstocked on slow movers and short on fast ones. Group SKUs by supplier lead time first, since that is usually the biggest driver, then adjust safety days up for items with unpredictable demand or unreliable suppliers.

Watch for a cash and shelf space tradeoff

More days of stock means more cash tied up and more storage space used. Less days of stock means more frequent orders and higher risk of running out. Many small stores err on the side of too much safety stock because stockouts feel worse than overstock, but overstock quietly eats cash every month. Review your days of stock target per SKU every few months, especially after a sales trend shifts.

Seasonal and new items need special handling

New products do not have enough sales history to calculate a reliable daily sales rate, so start conservative and adjust once you have a few weeks of real data. Seasonal items need higher cover heading into their peak and lower cover coming out of it, which a flat days-of-stock rule will not catch on its own.

Step by step

  1. List each SKU with its supplier and that supplier's lead time in days
  2. Set a safety day buffer per supplier based on how reliable their delivery actually is
  3. Add lead time plus safety days to get your reorder point in days of stock
  4. Multiply that by the SKU's average daily sales to get your reorder point in units
  5. Check current on-hand plus on-order units against that reorder point weekly
  6. Raise safety days for SKUs that have stocked out recently or sell unevenly
  7. Lower days of cover for slow movers tying up cash on the shelf

Worked example

Say a supplier has a 14-day lead time and you add 5 safety days for shipping delays, giving 19 days of stock as your reorder point. If the SKU sells 6 units a day on average, your reorder point is 6 x 19 = 114 units. Once on-hand plus on-order drops to 114 units or below, it is time to reorder, and your order quantity should cover lead time plus however many days of cover you want to hold, minus what you already have on hand or on order.

How SteadyShelf helps

SteadyShelf calculates this reorder point automatically per SKU, using each supplier's lead time and safety days along with a rolling sales average, so you do not have to track it in a spreadsheet. It will not tell you the ideal days-of-stock policy for your business or weigh cash flow against stockout risk for you; that judgment call is still yours, especially for new or seasonal items without enough history.

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

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FAQ

Should I use the same days of stock for every product?

No. Products with long supplier lead times or unreliable demand need more days of cover, while fast-moving items from quick suppliers can run leaner. Set the target per SKU or at least per supplier, not store-wide.

How do I set days of stock for a brand new product with no sales history?

Start conservative, using a comparable existing product as a rough guide, and order a smaller initial quantity. Once you have a few weeks of real sales data, recalculate the reorder point using actual daily sales instead of a guess.

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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