Inventory glossary
What is Average daily sales?
Average daily sales is the typical number of units of a product you sell per day, calculated over a chosen period.
Average daily sales is the building block for almost every reorder decision. Once you know how many units move per day, you can work out how many days of stock you have left, when to reorder, and how much safety stock you need to cover slow or fast spells.
Use it by picking a recent period that reflects normal demand, not a one-off sale or an out-of-stock week, and dividing total units sold by the number of days in that period. Recalculate it regularly, since sales pace changes with seasons, promotions and growth.
Formula
Example
A candle store sold 210 units of its lavender candle over the last 30 days. Average daily sales = 210 / 30 = 7 units per day. If they have 56 units in stock, that is 56 / 7 = 8 days of stock left.
Common mistakes
- Using a period that includes a stockout, which understates real demand.
- Including a one-time promo or wholesale order that skews the average upward.
- Never updating the number as sales trends shift, so reorder points go stale.
Average daily sales and SteadyShelf
SteadyShelf calculates average daily sales per variant automatically and uses it to forecast when each SKU will run out and when to order more.
SteadyShelf is launching on the Shopify App Store. Join early access to get the install link first.
Related terms
Reorder point · Days of supply · Lead time demand · Safety stock · Demand forecasting
FAQ
How many days of sales should I use to calculate average daily sales?
Most small stores use 30 to 90 days. Shorter periods react faster to recent trends but are noisier. Longer periods smooth out noise but react slower to real changes in demand.
Should I exclude days when a product was out of stock?
Yes. Days with no stock show zero sales that have nothing to do with demand. Including them makes your average daily sales look lower than actual customer 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.
Get early access