Free tool
Days of stock left calculator (stock cover)
How long will your stock last? Enter recent sales and what you have, and see your runway compared to your supplier's lead time.
The formula
Use recent sales (the last 4 weeks is a good default) and skip days the product was out of stock, or the pace will look slower than it really is.
The number that actually matters
Days of stock on its own doesn't tell you to act. Compare it with the supplier's lead time. 40 days of stock sounds safe, but with a 45-day lead time you're already 5 days late. Add safety stock and that becomes your reorder point. Not sure how big the buffer should be? Use the safety stock calculator.
FAQ
What is days of stock (stock cover)?
How many days your current inventory will last at your current sales pace: units available divided by average units sold per day.
How many days of stock should I hold?
At minimum, your supplier lead time plus a safety buffer. Below that, you can't get new stock in before you run out. Much more than lead time plus your order cycle usually means cash tied up for no reason.
Does Shopify show days of inventory remaining?
Shopify's inventory reports include a days of inventory remaining report on eligible plans. It doesn't compare that number to each supplier's lead time, which is what tells you when to order.
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