Walmart.com picked an optimal box-size mix, cutting $600K a year and projecting $2M.

Walmart's online business grew quickly after 2006, so it built distribution centres to ship orders sold on Walmart.com. The Carrollton, Georgia DC handled a large share of orders sent to customers or to stores for pickup.

Because carton sizes were chosen by habit, the DC shipped orders in ill-fitting boxes, wasting material and shipping volume and driving up labour.

In spring 2011 the DC ran a cost-improvement project to optimise its carton mix. Working with managers and the corporate supply-chain team, analysts built an Excel-based algorithm to determine the optimal sizes for four automated and six manual cartons.

Walmart fully implemented the algorithm as a decision-support system for reconfiguring the mix, certifying $600,000 a year in order-fulfilment savings and projecting $2 million a year across the network.