A WooCommerce merchant quotes a FedEx rate on Tuesday, and the same shipment costs more if it processes on Thursday; nothing changed on the merchant’s end; the fuel surcharge simply updated mid-week. For stores shipping regular FedEx volume, understanding exactly when and how that number moves is the difference between shipping costs that make sense and ones that seem to shift for no reason. This guide explains how FedEx fuel surcharges actually work, how they differ across Ground, Express, and Freight, why the update cycle runs on a different day than UPS, and how the FedEx Shipping Plugin for WooCommerce with Print Label handles it at checkout. It exists to pass fluctuating fuel costs through to shippers, and because it’s calculated as a percentage, it scales with shipment cost; a WooCommerce store shipping heavier or higher-value packages carries a proportionally larger fuel surcharge in absolute dollars than one shipping small, low-cost parcels. How FedEx Calculates the Fuel Surcharge on WooCommerce Orders FedEx reviews its fuel index every Monday, using the U.