Overselling costs ecommerce sellers more than just a single sale—it damages customer trust, triggers platform penalties, and eats into profits through refund fees and negative reviews. In 2026, with sellers operating across Shopee, Lazada, TikTok Shop, and Shopify simultaneously, manual inventory tracking isn’t just difficult—it’s impossible.

The safety stock formula helps you determine the extra inventory you need to keep on hand to avoid stockouts. A common method is (Maximum Daily Sales × Maximum Lead Time) – (Average Daily Sales × Average Lead Time). This isn’t just theory; it’s a practical calculation that provides a data-backed buffer to protect your sales and maintain customer satisfaction.

A perpetual stock system is an inventory management method that gives you a real-time, continuous count of every single item you own. Every sale, return, or new shipment instantly updates your total stock levels, so you always have a live, accurate view of your inventory.

Running out of stock is a direct blow to your sales and your ranking on competitive marketplaces. A proper safety stock computation is your strategic buffer, the cushion that protects you from a sudden spike in demand or an unexpected delay from your supplier. Think of it as an insurance policy for your revenue stream.

A simple way to calculate a basic safety stock buffer is with this formula: (Maximum Daily Sales × Maximum Lead Time) – (Average Daily Sales × Average Lead Time). This gives you a baseline cushion to protect your ecommerce business from sudden sales spikes and supplier delays, helping you avoid painful stockouts.

In e-commerce, lead time is the total time it takes from when a customer clicks ‘buy’ to when the package is in their hands. It’s the entire waiting period, covering every single step in between. Getting this number as low as possible is a sure sign of an efficient, customer-focused operation.