Inventory is where an e-commerce store’s cash actually lives, and these calculators answer its three standing questions: how long current stock will last, when to order more, and how much to order. The weeks of supply calculator answers the first, dividing on-hand units by weekly sales; most DTC stores aim to hold roughly 4–8 weeks. That number feeds directly into reorder timing, because a SKU with six weeks of supply and a four-week lead time is only two weeks from its trigger.
The reorder point calculator makes that trigger exact: daily sales times lead time, plus safety stock for demand spikes and late shipments. The EOQ calculator then sizes the order itself, balancing per-order costs against the holding cost of stock that sits. Timing and quantity are separate decisions, and merchants who merge them usually either stock out or over-order.
The rest of the suite audits how well the system runs. Turnover and days of inventory measure speed, sell-through grades a season’s buy, and the inventory shrinkage calculator prices the gap between counted and recorded stock, typically 1–2% of inventory value lost to damage, miscounts, and theft. Dead stock and stockout tools price the cost of getting the balance wrong in either direction.
Frequently asked questions
How much inventory should an e-commerce store hold?
Most DTC stores target 4–8 weeks of supply per SKU: enough to absorb a demand spike or a late shipment without parking months of cash on shelves. Stretch toward 10–12 weeks ahead of Q4 or with long overseas lead times, and shrink it with fast domestic replenishment. Compute it per SKU from actual weekly sales; a storewide average hides the risk.
When should I reorder inventory?
When stock hits the reorder point: average daily sales multiplied by supplier lead time in days, plus safety stock. Selling 20 units a day on a 14-day lead time with 60 units of buffer means reordering at 340 units. Recalculate monthly, and more often in Q4, because a reorder point set on January’s sales rate triggers far too late in November.
What is a normal inventory shrinkage rate?
US retail shrinkage averages around 1.5% of inventory value, and anything under 1% is good for an e-commerce operation. Shrinkage is the gap between what records say you own and what a physical count finds, covering theft, damage, receiving errors, and miscounts. If yours runs above 2–3%, audit receiving first; in warehouses, paperwork errors usually beat theft.
What is a good inventory turnover ratio?
Most healthy e-commerce stores turn inventory 4–8 times a year, which means 45–90 days of stock on hand. Fashion and consumables should run faster; heavy or seasonal goods run slower. Below 3 turns, cash is sleeping in the warehouse while holding costs of 20–30% of inventory value per year eat the margin. Above 10, check whether stockouts are capping sales.
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