Days of Inventory Calculator

A workable floor is your full supplier lead time plus safety-stock days — typically 45–90 days for merchants importing from overseas, and 20–40 for those restocking domestically. Below that you will stock out on any hiccup; far above it (120+ days) you are financing a warehouse of cash that could be funding growth instead.

They are reciprocals: days of inventory = 365 ÷ turnover, and turnover = 365 ÷ days. Six turns a year is 61 days on hand; 30 days on hand is 12.2 turns. Use days when planning purchase orders and cash (a calendar is intuitive), and turns when comparing efficiency across periods or against other stores.

Both, for different jobs. The store-wide figure drives cash-flow planning and shows the trend. The per-SKU figure is where the action is: a healthy 60-day average routinely hides A-sellers at 15 days about to stock out and dead SKUs at 400 days. Rank SKUs by days on hand monthly and act on both tails of the list.

Your shelf is valued at cost, so the burn rate must be at cost too. Dividing inventory-at-cost by revenue-per-day understates your true days on hand by your margin percentage — a 50%-margin store would appear to hold half the days it really does, and would over-order to compensate. Keep both numbers at cost and the answer is honest.